connector.py

from transformers import PretrainedConfig, PreTrainedModel

import inspect
import math
from dataclasses import dataclass
from typing import Dict, List, Optional, Tuple, Union
import json

import torch
import torch.nn.functional as F
import torch.utils.checkpoint
from torch import nn
from torch.nn import CrossEntropyLoss

from transformers.activations import ACT2FN
from transformers.cache_utils import Cache, DynamicCache
from transformers.modeling_attn_mask_utils import _prepare_4d_attention_mask
from transformers.modeling_outputs import BaseModelOutput, ModelOutput
from transformers.utils import (
    add_start_docstrings,
    add_start_docstrings_to_model_forward,
    is_flash_attn_2_available,
    is_flash_attn_greater_or_equal_2_10,
    logging,
    replace_return_docstrings,
)

if is_flash_attn_2_available():
    from flash_attn import flash_attn_func, flash_attn_varlen_func
    from flash_attn.bert_padding import index_first_axis, pad_input, unpad_input  # noqa

    _flash_supports_window_size = "window_size" in list(inspect.signature(flash_attn_func).parameters)

# Copied from transformers.models.llama.modeling_llama.repeat_kv
def repeat_kv(hidden_states: torch.Tensor, n_rep: int) -> torch.Tensor:
    """
    This is the equivalent of torch.repeat_interleave(x, dim=1, repeats=n_rep). The hidden states go from (batch,
    num_key_value_heads, seqlen, head_dim) to (batch, num_attention_heads, seqlen, head_dim)
    """
    batch, num_key_value_heads, slen, head_dim = hidden_states.shape
    if n_rep == 1:
        return hidden_states
    hidden_states = hidden_states[:, :, None, :, :].expand(batch, num_key_value_heads, n_rep, slen, head_dim)
    return hidden_states.reshape(batch, num_key_value_heads * n_rep, slen, head_dim)

class Idefics2ConnectorConfig(PretrainedConfig):
    r"""
    Configuration objects inherit from [`PretrainedConfig`] and can be used to control the model outputs. Read the
    documentation from [`PretrainedConfig`] for more information.

    Args:
        hidden_act (`str` or `function`, *optional*, defaults to `"silu"`):
            The non-linear activation function (function or string) in the perceiver block.
        resampler_n_latents (`int`, *optional*, defaults to 64):
            Number of latent embeddings to resample ("compress") the input sequence to (usually < 128).
        resampler_depth (`int`, *optional*, defaults to 3):
            Depth of the Perceiver Resampler (Transformer w/ cross attention). Should be shallow (<= 3).
        resampler_n_heads (`int`, *optional*, defaults to 16):
            Number of heads in each Transformer block (for multi-headed self-attention).
        resampler_head_dim (`int`, *optional*, defaults to 96):
            Dimensionality of each head projection in the Transformer block.
        num_key_value_heads (`int`, *optional*, defaults to 4):
            Number of key-value heads in the perceiver attention block.
        attention_dropout (`float`, *optional*, defaults to 0.0):
            The dropout ratio for the attention probabilities.
    """
    _auto_class = 'AutoConfig'
    model_type = "Idefics2ConnectorConfig"

    def __init__(
        self,
        vision_hidden_size=1152,
        hidden_size=4096,
        hidden_act="silu",
        resampler_n_latents=64,
        resampler_depth=3,
        rms_norm_eps=1e-05,
        resampler_n_heads=16,
        resampler_head_dim=96,
        num_key_value_heads=4,
        attention_dropout=0.0,
        intermediate_size=14336,
        **kwargs,
    ):
        super().__init__(**kwargs)
        self.vision_hidden_size = vision_hidden_size
        self.hidden_size = hidden_size
        self.hidden_act = hidden_act
        self.resampler_n_latents = resampler_n_latents
        self.resampler_depth = resampler_depth
        self.rms_norm_eps = rms_norm_eps
        self.resampler_n_heads = resampler_n_heads
        self.num_key_value_heads = num_key_value_heads
        self.resampler_head_dim = resampler_head_dim
        self.attention_dropout = attention_dropout
        self.intermediate_size = intermediate_size
        if self.num_key_value_heads > self.resampler_n_heads:
            raise ValueError(
                f"num_key_value_heads={self.num_key_value_heads} must be less than or equal to"
                f" resampler_n_heads={self.resampler_n_heads}"
            )
        

    @classmethod
    def from_pretrained(cls, config_path, **kwargs) -> "PretrainedConfig":
        
        with open(config_path, "r", encoding="utf-8") as f:
            config_dict = json.load(f)
        cls = Idefics2ConnectorConfig(
            vision_hidden_size=config_dict['vision_hidden_size'],
            hidden_size=config_dict['hidden_size'],
            hidden_act="silu",
            resampler_n_latents=config_dict['resampler_n_latents'],
            resampler_depth=config_dict['resampler_depth'],
            rms_norm_eps=config_dict['rms_norm_eps'],
            intermediate_size = config_dict['intermediate_size']
        )
        
        return cls

# Copied from transformers.models.llama.modeling_llama._get_unpad_data
def _get_unpad_data(attention_mask):
    seqlens_in_batch = attention_mask.sum(dim=-1, dtype=torch.int32)
    indices = torch.nonzero(attention_mask.flatten(), as_tuple=False).flatten()
    max_seqlen_in_batch = seqlens_in_batch.max().item()
    cu_seqlens = F.pad(torch.cumsum(seqlens_in_batch, dim=0, dtype=torch.int32), (1, 0))
    return (
        indices,
        cu_seqlens,
        max_seqlen_in_batch,
    )

class Idefics2PerceiverAttention(nn.Module):
    def __init__(self, config, layer_idx: Optional[int] = None) -> None:
        """Perceiver Cross-Attention Module --> let long-form inputs be `context`, resampled embeddings be `latents`"""
        super().__init__()

        self.layer_idx = None
        self.hidden_size = config.hidden_size
        self.num_heads = config.resampler_n_heads
        self.head_dim = config.resampler_head_dim
        self.num_key_value_heads = config.num_key_value_heads
        self.num_key_value_groups = self.num_heads // self.num_key_value_heads
        self.attention_dropout = config.attention_dropout

        self.q_proj = nn.Linear(self.hidden_size, self.num_heads * self.head_dim, bias=False)
        self.k_proj = nn.Linear(self.hidden_size, self.num_key_value_heads * self.head_dim, bias=False)
        self.v_proj = nn.Linear(self.hidden_size, self.num_key_value_heads * self.head_dim, bias=False)
        self.o_proj = nn.Linear(self.num_heads * self.head_dim, self.hidden_size, bias=False)

        self.is_causal = False

    def forward(
        self,
        latents: torch.Tensor,
        context: torch.Tensor,
        attention_mask: Optional[torch.Tensor] = None,
        position_ids: Optional[torch.LongTensor] = None,
        past_key_value: Optional[Tuple[torch.Tensor]] = None,
        output_attentions: bool = False,
        use_cache: bool = False,
    ) -> Tuple[torch.Tensor, Optional[torch.Tensor], Optional[Tuple[torch.Tensor]]]:
        """
        Runs Perceiver Self-Attention, with special (context, latents) appended along the `seq` dimension!

        Args:
            latents (`torch.Tensor`): Tensor of shape [bsz, n_latents, embed_dim] representing fixed length latents to compress to.
            context (`torch.Tensor`): Tensor of shape [bsz, seq, embed_dim] representing long-form context to resample.
            attention_mask (`torch.Tensor`, *optional*): Tensor of shape [bsz, 1, seq, n_latents] representing attention mask.
            position_ids (`torch.LongTensor`, *optional*): Tensor of shape [bsz, seq] representing position indices of each input token.
            past_key_value (`Tuple[torch.Tensor]`, *optional*): Tuple of tensors containing cached key and value states.
            output_attentions (`bool`, *optional*, defaults to `False`): Whether to return attention weights.
            use_cache (`bool`, *optional*, defaults to `False`): Whether to use past_key_value for caching.
        """
        bsz, q_len, _ = latents.size()
        kv_seq_len = q_len + context.size()[1]

        hidden_states = torch.concat([context, latents], dim=-2)

        query_states = self.q_proj(latents)
        key_states = self.k_proj(hidden_states)
        value_states = self.v_proj(hidden_states)

        query_states = query_states.view(bsz, q_len, self.num_heads, self.head_dim).transpose(1, 2)
        key_states = key_states.view(bsz, kv_seq_len, self.num_key_value_heads, self.head_dim).transpose(1, 2)
        value_states = value_states.view(bsz, kv_seq_len, self.num_key_value_heads, self.head_dim).transpose(1, 2)

        past_key_value = getattr(self, "past_key_value", past_key_value)

        if past_key_value is not None:
            key_states, value_states = past_key_value.update(key_states, value_states, self.layer_idx)

        # repeat k/v heads if n_kv_heads < n_heads
        key_states = repeat_kv(key_states, self.num_key_value_groups)
        value_states = repeat_kv(value_states, self.num_key_value_groups)

        attn_weights = torch.matmul(query_states, key_states.transpose(2, 3)) / math.sqrt(self.head_dim)

        if attn_weights.size() != (bsz, self.num_heads, q_len, kv_seq_len):
            raise ValueError(
                f"Attention weights should be of size {(bsz, self.num_heads, q_len, kv_seq_len)}, but is"
                f" {attn_weights.size()}"
            )

        if attention_mask is not None:
            if attention_mask.size() != (bsz, 1, q_len, kv_seq_len):
                raise ValueError(
                    f"Attention mask should be of size {(bsz, 1, q_len, kv_seq_len)}, but is {attention_mask.size()}"
                )

            attn_weights = attn_weights + attention_mask

        # upcast attention to fp32
        attn_weights = nn.functional.softmax(attn_weights, dim=-1, dtype=torch.float32).to(query_states.dtype)
        attn_output = torch.matmul(attn_weights, value_states)

        if attn_output.size() != (bsz, self.num_heads, q_len, self.head_dim):
            raise ValueError(
                f"`attn_output` should be of size {(bsz, self.num_heads, q_len, self.head_dim)}, but is"
                f" {attn_output.size()}"
            )

        attn_output = attn_output.transpose(1, 2).contiguous()
        attn_output = attn_output.reshape(bsz, q_len, self.num_heads * self.head_dim)

        attn_output = self.o_proj(attn_output)

        if not output_attentions:
            attn_weights = None

        return attn_output, attn_weights, past_key_value

# Copied from transformers.models.mistral.modeling_mistral.MistralFlashAttention2 with MistralAttention->Idefics2PerceiverAttention,MistralFlashAttention->Idefics2PerceiverFlashAttention,Mistral->Idefics2
class Idefics2PerceiverFlashAttention2(Idefics2PerceiverAttention):
    """
    Idefics2 flash attention module. This module inherits from `Idefics2PerceiverAttention` as the weights of the module stays
    untouched. The only required change would be on the forward pass where it needs to correctly call the public API of
    flash attention and deal with padding tokens in case the input contains any of them.
    """

    # Copied from transformers.models.llama.modeling_llama.LlamaFlashAttention2.__init__
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        # TODO: Should be removed once Flash Attention for RoCm is bumped to 2.1.
        # flash_attn<2.1 generates top-left aligned causal mask, while what is needed here is bottom-right alignement, that was made default for flash_attn>=2.1. This attribute is used to handle this difference. Reference: https://github.com/Dao-AILab/flash-attention/releases/tag/v2.1.0.
        # Beware that with flash_attn<2.1, using q_seqlen != k_seqlen (except for the case q_seqlen == 1) produces a wrong mask (top-left).
        self._flash_attn_uses_top_left_mask = not is_flash_attn_greater_or_equal_2_10()

    # Ignore copy
    def forward(
        self,
        latents: torch.Tensor,
        context: torch.Tensor,
        attention_mask: Optional[torch.LongTensor] = None,
        position_ids: Optional[torch.LongTensor] = None,
        past_key_value: Optional[Cache] = None,
        output_attentions: bool = False,
        use_cache: bool = False,
        **kwargs,
    ) -> Tuple[torch.Tensor, Optional[torch.Tensor], Optional[Tuple[torch.Tensor]]]:
        
        bsz, q_len, _ = latents.size()
        kv_seq_len = q_len + context.size()[1]

        # Query, Key, Value Projections --> Note that in Flamingo, latents are *concatenated* with context prior to attn!
        #   Note: This results in queries w/ `seq = n_latents`, and keys, values with `seq = len(context) + n_latents`
        query_states = self.q_proj(latents)
        key_states = self.k_proj(torch.cat([context, latents], dim=-2))
        value_states = self.v_proj(torch.cat([context, latents], dim=-2))

        query_states = query_states.view(bsz, q_len, self.num_heads, self.head_dim).transpose(1, 2)
        key_states = key_states.view(bsz, kv_seq_len, self.num_key_value_heads, self.head_dim).transpose(1, 2)
        value_states = value_states.view(bsz, kv_seq_len, self.num_key_value_heads, self.head_dim).transpose(1, 2)

        kv_seq_len = key_states.shape[-2]
        if past_key_value is not None:
            kv_seq_len += past_key_value[0].shape[-2]

        if past_key_value is not None:
            # Activate slicing cache only if the config has a value `sliding_windows` attribute
            if hasattr(self.config, "sliding_window") and kv_seq_len > self.config.sliding_window:
                slicing_tokens = kv_seq_len - self.config.sliding_window

                past_key = past_key_value[0]
                past_value = past_key_value[1]

                past_key = past_key[:, :, slicing_tokens:, :].contiguous()
                past_value = past_value[:, :, slicing_tokens:, :].contiguous()

                if past_key.shape[-2] != self.config.sliding_window - 1:
                    raise ValueError(
                        "past key must have a shape of (`batch_size, num_heads, self.config.sliding_window-1,"
                        f" head_dim`), got {past_key.shape}"
                    )

                past_key_value = (past_key, past_value)

                if attention_mask is not None:
                    attention_mask = attention_mask[:, slicing_tokens:]
                    attention_mask = torch.cat([attention_mask, torch.ones_like(attention_mask[:, -1:])], dim=-1)

            key_states = torch.cat([past_key_value[0], key_states], dim=2)
            value_states = torch.cat([past_key_value[1], value_states], dim=2)

        past_key_value = (key_states, value_states) if use_cache else None

        # repeat k/v heads if n_kv_heads < n_heads
        key_states = repeat_kv(key_states, self.num_key_value_groups)
        value_states = repeat_kv(value_states, self.num_key_value_groups)
        dropout_rate = 0.0 if not self.training else self.attention_dropout

        # In PEFT, usually we cast the layer norms in float32 for training stability reasons
        # therefore the input hidden states gets silently casted in float32. Hence, we need
        # cast them back in float16 just to be sure everything works as expected.
        input_dtype = query_states.dtype
        if input_dtype == torch.float32:
            if torch.is_autocast_enabled():
                target_dtype = torch.get_autocast_gpu_dtype()
            # Handle the case where the model is quantized
            elif hasattr(self.config, "_pre_quantization_dtype"):
                target_dtype = self.config._pre_quantization_dtype
            else:
                target_dtype = self.q_proj.weight.dtype

            logger.warning_once(
                f"The input hidden states seems to be silently casted in float32, this might be related to"
                f" the fact you have upcasted embedding or layer norm layers in float32. We will cast back the input in"
                f" {target_dtype}."
            )

            query_states = query_states.to(target_dtype)
            key_states = key_states.to(target_dtype)
            value_states = value_states.to(target_dtype)

        # Reashape to the expected shape for Flash Attention
        query_states = query_states.transpose(1, 2)
        key_states = key_states.transpose(1, 2)
        value_states = value_states.transpose(1, 2)

        attn_output = self._flash_attention_forward(
            query_states,
            key_states,
            value_states,
            attention_mask,
            q_len,
            dropout=dropout_rate,
            use_sliding_windows=False,
        )

        attn_output = attn_output.reshape(bsz, q_len, self.num_heads * self.head_dim).contiguous()
        attn_output = self.o_proj(attn_output)

        if not output_attentions:
            attn_weights = None

        return attn_output, attn_weights, past_key_value

    def _flash_attention_forward(
        self,
        query_states,
        key_states,
        value_states,
        attention_mask,
        query_length,
        dropout=0.0,
        softmax_scale=None,
        use_sliding_windows=False,
    ):
        """
        Calls the forward method of Flash Attention - if the input hidden states contain at least one padding token
        first unpad the input, then computes the attention scores and pad the final attention scores.

        Args:
            query_states (`torch.Tensor`):
                Input query states to be passed to Flash Attention API
            key_states (`torch.Tensor`):
                Input key states to be passed to Flash Attention API
            value_states (`torch.Tensor`):
                Input value states to be passed to Flash Attention API
            attention_mask (`torch.Tensor`):
                The padding mask - corresponds to a tensor of size `(batch_size, seq_len)` where 0 stands for the
                position of padding tokens and 1 for the position of non-padding tokens.
            dropout (`float`):
                Attention dropout
            softmax_scale (`float`, *optional*):
                The scaling of QK^T before applying softmax. Default to 1 / sqrt(head_dim)
            use_sliding_windows (`bool`, *optional*):
                Whether to activate sliding window attention.
        """
        if not self._flash_attn_uses_top_left_mask:
            causal = self.is_causal
        else:
            # TODO: Remove the `query_length != 1` check once Flash Attention for RoCm is bumped to 2.1. For details, please see the comment in LlamaFlashAttention2 __init__.
            causal = self.is_causal and query_length != 1

        # Contains at least one padding token in the sequence
        if attention_mask is not None:
            batch_size = query_states.shape[0]
            query_states, key_states, value_states, indices_q, cu_seq_lens, max_seq_lens = self._upad_input(
                query_states, key_states, value_states, attention_mask, query_length
            )

            cu_seqlens_q, cu_seqlens_k = cu_seq_lens
            max_seqlen_in_batch_q, max_seqlen_in_batch_k = max_seq_lens

            if not use_sliding_windows:
                attn_output_unpad = flash_attn_varlen_func(
                    query_states,
                    key_states,
                    value_states,
                    cu_seqlens_q=cu_seqlens_q,
                    cu_seqlens_k=cu_seqlens_k,
                    max_seqlen_q=max_seqlen_in_batch_q,
                    max_seqlen_k=max_seqlen_in_batch_k,
                    dropout_p=dropout,
                    softmax_scale=softmax_scale,
                    causal=causal,
                )
            else:
                attn_output_unpad = flash_attn_varlen_func(
                    query_states,
                    key_states,
                    value_states,
                    cu_seqlens_q=cu_seqlens_q,
                    cu_seqlens_k=cu_seqlens_k,
                    max_seqlen_q=max_seqlen_in_batch_q,
                    max_seqlen_k=max_seqlen_in_batch_k,
                    dropout_p=dropout,
                    softmax_scale=softmax_scale,
                    causal=causal,
                    window_size=(self.config.sliding_window, self.config.sliding_window),
                )

            attn_output = pad_input(attn_output_unpad, indices_q, batch_size, query_length)
        else:
            if not use_sliding_windows:
                attn_output = flash_attn_func(
                    query_states,
                    key_states,
                    value_states,
                    dropout,
                    softmax_scale=softmax_scale,
                    causal=causal,
                )
            else:
                attn_output = flash_attn_func(
                    query_states,
                    key_states,
                    value_states,
                    dropout,
                    softmax_scale=softmax_scale,
                    causal=causal,
                    window_size=(self.config.sliding_window, self.config.sliding_window),
                )

        return attn_output

    def _upad_input(self, query_layer, key_layer, value_layer, attention_mask, query_length):
        batch_size, kv_seq_len, num_heads, head_dim = key_layer.shape

        # On the first iteration we need to properly re-create the padding mask
        # by slicing it on the proper place
        if kv_seq_len != attention_mask.shape[-1]:
            attention_mask_num_tokens = attention_mask.shape[-1]
            attention_mask = attention_mask[:, attention_mask_num_tokens - kv_seq_len :]

        indices_k, cu_seqlens_k, max_seqlen_in_batch_k = _get_unpad_data(attention_mask)

        key_layer = index_first_axis(key_layer.reshape(batch_size * kv_seq_len, num_heads, head_dim), indices_k)
        value_layer = index_first_axis(value_layer.reshape(batch_size * kv_seq_len, num_heads, head_dim), indices_k)

        if query_length == kv_seq_len:
            query_layer = index_first_axis(
                query_layer.reshape(batch_size * kv_seq_len, num_heads, head_dim), indices_k
            )
            cu_seqlens_q = cu_seqlens_k
            max_seqlen_in_batch_q = max_seqlen_in_batch_k
            indices_q = indices_k
        elif query_length == 1:
            max_seqlen_in_batch_q = 1
            cu_seqlens_q = torch.arange(
                batch_size + 1, dtype=torch.int32, device=query_layer.device
            )  # There is a memcpy here, that is very bad.
            indices_q = cu_seqlens_q[:-1]
            query_layer = query_layer.squeeze(1)
        else:
            # The -q_len: slice assumes left padding.
            attention_mask = attention_mask[:, -query_length:]
            query_layer, indices_q, cu_seqlens_q, max_seqlen_in_batch_q = unpad_input(query_layer, attention_mask)

        return (
            query_layer,
            key_layer,
            value_layer,
            indices_q,
            (cu_seqlens_q, cu_seqlens_k),
            (max_seqlen_in_batch_q, max_seqlen_in_batch_k),
        )

IDEFICS2_PERCEIVER_ATTENTION_CLASSES = {
    "eager": Idefics2PerceiverAttention,
    "flash_attention_2": Idefics2PerceiverFlashAttention2,
}


class Idefics2MLP(nn.Module):
    def __init__(
        self,
        hidden_size: int,
        intermediate_size: int,
        output_size: int,
        hidden_act: str,
    ):
        super().__init__()
        self.gate_proj = nn.Linear(hidden_size, intermediate_size, bias=False)
        self.up_proj = nn.Linear(hidden_size, intermediate_size, bias=False)
        self.down_proj = nn.Linear(intermediate_size, output_size, bias=False)
        self.act_fn = ACT2FN[hidden_act]

    def forward(self, x):
        return self.down_proj(self.act_fn(self.gate_proj(x)) * self.up_proj(x))

# Copied from transformers.models.llama.modeling_llama.LlamaRMSNorm with Llama->Idefics2
class Idefics2RMSNorm(nn.Module):
    def __init__(self, hidden_size, eps=1e-6):
        """
        Idefics2RMSNorm is equivalent to T5LayerNorm
        """
        super().__init__()
        self.weight = nn.Parameter(torch.ones(hidden_size))
        self.variance_epsilon = eps

    def forward(self, hidden_states):
        input_dtype = hidden_states.dtype
        hidden_states = hidden_states.to(torch.float32)
        variance = hidden_states.pow(2).mean(-1, keepdim=True)
        hidden_states = hidden_states * torch.rsqrt(variance + self.variance_epsilon)
        return self.weight * hidden_states.to(input_dtype)

class Idefics2PerceiverLayer(nn.Module):
    def __init__(self, config, layer_idx: int):
        super().__init__()
        self.hidden_size = config.hidden_size
        self.n_latents = config.resampler_n_latents
        self.depth = config.resampler_depth
        self.rms_norm_eps = config.rms_norm_eps

        self.input_latents_norm = Idefics2RMSNorm(self.hidden_size, eps=self.rms_norm_eps)
        self.input_context_norm = Idefics2RMSNorm(self.hidden_size, eps=self.rms_norm_eps)
        self.self_attn = IDEFICS2_PERCEIVER_ATTENTION_CLASSES[config._attn_implementation](config, layer_idx=layer_idx)
        self.post_attention_layernorm = Idefics2RMSNorm(self.hidden_size, eps=self.rms_norm_eps)
        self.mlp = Idefics2MLP(
            hidden_size=config.hidden_size,
            intermediate_size=config.hidden_size * 4,
            output_size=config.hidden_size,
            hidden_act=config.hidden_act,
        )

    def forward(
        self,
        latents: torch.Tensor,
        context: torch.Tensor,
        attention_mask: Optional[torch.Tensor] = None,
        position_ids: Optional[torch.LongTensor] = None,
        past_key_value: Optional[Tuple[torch.Tensor]] = None,
        output_attentions: Optional[bool] = False,
        use_cache: Optional[bool] = False,
        **kwargs,
    ) -> Tuple[torch.FloatTensor, Optional[Tuple[torch.FloatTensor, torch.FloatTensor]]]:
        """
        Args:
            latents (`torch.FloatTensor`): input to the layer of shape `(batch, seq_len, embed_dim)`
            context (`torch.FloatTensor`): input to the layer of shape `(batch, seq_len, embed_dim)`
            attention_mask (`torch.FloatTensor`, *optional*): attention mask of size
                `(batch, sequence_length)` where padding elements are indicated by 0.
            output_attentions (`bool`, *optional*):
                Whether or not to return the attentions tensors of all attention layers. See `attentions` under
                returned tensors for more detail.
            use_cache (`bool`, *optional*):
                If set to `True`, `past_key_values` key value states are returned and can be used to speed up decoding
                (see `past_key_values`).
            past_key_value (`Tuple(torch.FloatTensor)`, *optional*): cached past key and value projection states
        """
        residual = latents

        latents = self.input_latents_norm(latents)
        context = self.input_context_norm(context)

        latents, self_attn_weights, present_key_value = self.self_attn(
            latents=latents,
            context=context,
            attention_mask=attention_mask,
        )
        latents = residual + latents
        residual = latents

        latents = self.post_attention_layernorm(latents)
        latents = self.mlp(latents)
        latents = residual + latents

        outputs = (latents,)

        if output_attentions:
            outputs += (self_attn_weights,)

        if use_cache:
            outputs += (present_key_value,)

        return outputs

class Idefics2Qformer(nn.Module):
    
    def __init__(self, config) -> None:
        """
        Instantiates a Perceiver Resampler that operates over a sequence of embeddings (say from a ResNet or ViT or
        MAE) of a given dimension, performs `depth` blocks of cross-attention with a fixed `n_latents` inputs, then
        returns a Tensor of shape [bsz, n_latents, embed_dim]. The Resampler acts as a form of learned pooling and
        is derived from [Perceiver: General Perception with Iterative Attention](https://arxiv.org/abs/2103.03206).
        """
        super().__init__()
        config._attn_implementation = "flash_attention_2"
        self._use_flash_attention_2 = True
        
        self.hidden_size = config.hidden_size
        self.hidden_act = config.hidden_act
        self.n_latents = config.resampler_n_latents
        self.depth = config.resampler_depth
        self.rms_norm_eps = config.rms_norm_eps

        # Create Latents for Perceiver
        self.latents = nn.Parameter(torch.ones(self.n_latents, self.hidden_size))
        # Create Transformer Blocks
        self.layers = nn.ModuleList([Idefics2PerceiverLayer(config, idx) for idx in range(self.depth)])
        self.norm = Idefics2RMSNorm(self.hidden_size, eps=self.rms_norm_eps)

        
            

    def forward(
        self,
        context: torch.Tensor,
        attention_mask,
    ) -> torch.Tensor:
        # seq embed -> bsz seq embed
        latents = self.latents.unsqueeze(0).expand((context.shape[0], *self.latents.size()))

        latent_attention_mask = torch.ones(
            (attention_mask.size(0), latents.size(1)), dtype=attention_mask.dtype, device=attention_mask.device
        )
        attention_mask = torch.cat([attention_mask, latent_attention_mask], dim=-1)
        attention_mask = (
            _prepare_4d_attention_mask(attention_mask, latents.dtype, tgt_len=self.n_latents)
            if not self._use_flash_attention_2
            else attention_mask
        )
        #all_latents = []
        compressed_context = latents
        #all_latents.append(latents)
        for perceiver_layer in self.layers:
            layer_outputs = torch.utils.checkpoint.checkpoint(
                    perceiver_layer.__call__,
                    compressed_context,
                    context,
                    attention_mask,
                    None,
                    None,
                    False,
                    False,
                    use_reentrant=True)
            compressed_context = layer_outputs[0]
            #all_latents.append(compressed_context)

        compressed_context = self.norm(compressed_context)

        return compressed_context
    
class Idefics2Connector(PreTrainedModel):
    _auto_class = 'AutoModel'
    config_class = Idefics2ConnectorConfig
    
    def __init__(self, config):
        super().__init__(config)
        self.modality_projection = Idefics2MLP(
            hidden_size=config.vision_hidden_size,
            intermediate_size=config.intermediate_size,
            output_size=config.hidden_size,
            hidden_act=config.hidden_act,
        )
        self.perceiver_resampler = Idefics2Qformer(config)
        self.config = config

    def forward(self, image_hidden_states, attention_mask):
        image_hidden_states = self.modality_projection(image_hidden_states)
        image_hidden_states = self.perceiver_resampler(context=image_hidden_states, attention_mask=attention_mask)
        
        vision_hidden_size = image_hidden_states.shape[-1]
        num_image = image_hidden_states.shape[0]
        reshaped_image_hidden_states = image_hidden_states.view(num_image, -1, vision_hidden_size)
        
        return reshaped_image_hidden_states
    
    @classmethod
    def from_pretrained(self, config_path):
        config = Idefics2ConnectorConfig.from_pretrained(f'{config_path}/config.json')
        cls = Idefics2Connector(config=config)
        
        state_dict = torch.load(f'{config_path}/connector.pth', map_location='cpu')
        ret = cls.load_state_dict(state_dict, strict=False)
        print("Loading idefics2 Connector from : {}".format(config_path))
        return cls