diffusers/models/transformers/transformer_bria.py

import inspect
from typing import Any

import numpy as np
import torch
import torch.nn as nn
import torch.nn.functional as F

from ...configuration_utils import ConfigMixin, register_to_config
from ...loaders import FromOriginalModelMixin, PeftAdapterMixin
from ...utils import apply_lora_scale, logging
from ...utils.torch_utils import maybe_adjust_dtype_for_device, maybe_allow_in_graph
from ..attention import AttentionModuleMixin, FeedForward
from ..attention_dispatch import dispatch_attention_fn
from ..cache_utils import CacheMixin
from ..embeddings import TimestepEmbedding, apply_rotary_emb, get_timestep_embedding
from ..modeling_outputs import Transformer2DModelOutput
from ..modeling_utils import ModelMixin
from ..normalization import AdaLayerNormContinuous, AdaLayerNormZero, AdaLayerNormZeroSingle


logger = logging.get_logger(__name__)  # pylint: disable=invalid-name


def _get_projections(attn: "BriaAttention", hidden_states, encoder_hidden_states=None):
    query = attn.to_q(hidden_states)
    key = attn.to_k(hidden_states)
    value = attn.to_v(hidden_states)

    encoder_query = encoder_key = encoder_value = None
    if encoder_hidden_states is not None and attn.added_kv_proj_dim is not None:
        encoder_query = attn.add_q_proj(encoder_hidden_states)
        encoder_key = attn.add_k_proj(encoder_hidden_states)
        encoder_value = attn.add_v_proj(encoder_hidden_states)

    return query, key, value, encoder_query, encoder_key, encoder_value


def _get_fused_projections(attn: "BriaAttention", hidden_states, encoder_hidden_states=None):
    query, key, value = attn.to_qkv(hidden_states).chunk(3, dim=-1)

    encoder_query = encoder_key = encoder_value = (None,)
    if encoder_hidden_states is not None and hasattr(attn, "to_added_qkv"):
        encoder_query, encoder_key, encoder_value = attn.to_added_qkv(encoder_hidden_states).chunk(3, dim=-1)

    return query, key, value, encoder_query, encoder_key, encoder_value


def _get_qkv_projections(attn: "BriaAttention", hidden_states, encoder_hidden_states=None):
    if attn.fused_projections:
        return _get_fused_projections(attn, hidden_states, encoder_hidden_states)
    return _get_projections(attn, hidden_states, encoder_hidden_states)


def get_1d_rotary_pos_embed(
    dim: int,
    pos: np.ndarray | int,
    theta: float = 10000.0,
    use_real=False,
    linear_factor=1.0,
    ntk_factor=1.0,
    repeat_interleave_real=True,
    freqs_dtype=torch.float32,  #  torch.float32, torch.float64 (flux)
):
    """
    Precompute the frequency tensor for complex exponentials (cis) with given dimensions.

    This function calculates a frequency tensor with complex exponentials using the given dimension 'dim' and the end
    index 'end'. The 'theta' parameter scales the frequencies. The returned tensor contains complex values in complex64
    data type.

    Args:
        dim (`int`): Dimension of the frequency tensor.
        pos (`np.ndarray` or `int`): Position indices for the frequency tensor. [S] or scalar
        theta (`float`, *optional*, defaults to 10000.0):
            Scaling factor for frequency computation. Defaults to 10000.0.
        use_real (`bool`, *optional*):
            If True, return real part and imaginary part separately. Otherwise, return complex numbers.
        linear_factor (`float`, *optional*, defaults to 1.0):
            Scaling factor for the context extrapolation. Defaults to 1.0.
        ntk_factor (`float`, *optional*, defaults to 1.0):
            Scaling factor for the NTK-Aware RoPE. Defaults to 1.0.
        repeat_interleave_real (`bool`, *optional*, defaults to `True`):
            If `True` and `use_real`, real part and imaginary part are each interleaved with themselves to reach `dim`.
            Otherwise, they are concateanted with themselves.
        freqs_dtype (`torch.float32` or `torch.float64`, *optional*, defaults to `torch.float32`):
            the dtype of the frequency tensor.
    Returns:
        `torch.Tensor`: Precomputed frequency tensor with complex exponentials. [S, D/2]
    """
    assert dim % 2 == 0

    if isinstance(pos, int):
        pos = torch.arange(pos)
    if isinstance(pos, np.ndarray):
        pos = torch.from_numpy(pos)  # type: ignore  # [S]

    theta = theta * ntk_factor
    freqs = (
        1.0
        / (theta ** (torch.arange(0, dim, 2, dtype=freqs_dtype, device=pos.device)[: (dim // 2)] / dim))
        / linear_factor
    )  # [D/2]
    freqs = torch.outer(pos, freqs)  # type: ignore   # [S, D/2]
    if use_real and repeat_interleave_real:
        # bria
        freqs_cos = freqs.cos().repeat_interleave(2, dim=1).float()  # [S, D]
        freqs_sin = freqs.sin().repeat_interleave(2, dim=1).float()  # [S, D]
        return freqs_cos, freqs_sin
    elif use_real:
        # stable audio, allegro
        freqs_cos = torch.cat([freqs.cos(), freqs.cos()], dim=-1).float()  # [S, D]
        freqs_sin = torch.cat([freqs.sin(), freqs.sin()], dim=-1).float()  # [S, D]
        return freqs_cos, freqs_sin
    else:
        # lumina
        freqs_cis = torch.polar(torch.ones_like(freqs), freqs)  # complex64     # [S, D/2]
        return freqs_cis


class BriaAttnProcessor:
    _attention_backend = None
    _parallel_config = None

    def __init__(self):
        if not hasattr(F, "scaled_dot_product_attention"):
            raise ImportError(f"{self.__class__.__name__} requires PyTorch 2.0. Please upgrade your pytorch version.")

    def __call__(
        self,
        attn: "BriaAttention",
        hidden_states: torch.Tensor,
        encoder_hidden_states: torch.Tensor = None,
        attention_mask: torch.Tensor | None = None,
        image_rotary_emb: torch.Tensor | None = None,
    ) -> torch.Tensor:
        query, key, value, encoder_query, encoder_key, encoder_value = _get_qkv_projections(
            attn, hidden_states, encoder_hidden_states
        )

        query = query.unflatten(-1, (attn.heads, -1))
        key = key.unflatten(-1, (attn.heads, -1))
        value = value.unflatten(-1, (attn.heads, -1))

        query = attn.norm_q(query)
        key = attn.norm_k(key)

        if attn.added_kv_proj_dim is not None:
            encoder_query = encoder_query.unflatten(-1, (attn.heads, -1))
            encoder_key = encoder_key.unflatten(-1, (attn.heads, -1))
            encoder_value = encoder_value.unflatten(-1, (attn.heads, -1))

            encoder_query = attn.norm_added_q(encoder_query)
            encoder_key = attn.norm_added_k(encoder_key)

            query = torch.cat([encoder_query, query], dim=1)
            key = torch.cat([encoder_key, key], dim=1)
            value = torch.cat([encoder_value, value], dim=1)

        if image_rotary_emb is not None:
            query = apply_rotary_emb(query, image_rotary_emb, sequence_dim=1)
            key = apply_rotary_emb(key, image_rotary_emb, sequence_dim=1)

        hidden_states = dispatch_attention_fn(
            query,
            key,
            value,
            attn_mask=attention_mask,
            backend=self._attention_backend,
            parallel_config=self._parallel_config,
        )
        hidden_states = hidden_states.flatten(2, 3)
        hidden_states = hidden_states.to(query.dtype)

        if encoder_hidden_states is not None:
            encoder_hidden_states, hidden_states = hidden_states.split_with_sizes(
                [encoder_hidden_states.shape[1], hidden_states.shape[1] - encoder_hidden_states.shape[1]], dim=1
            )
            hidden_states = attn.to_out[0](hidden_states)
            hidden_states = attn.to_out[1](hidden_states)
            encoder_hidden_states = attn.to_add_out(encoder_hidden_states)

            return hidden_states, encoder_hidden_states
        else:
            return hidden_states


class BriaAttention(torch.nn.Module, AttentionModuleMixin):
    _default_processor_cls = BriaAttnProcessor
    _available_processors = [
        BriaAttnProcessor,
    ]

    def __init__(
        self,
        query_dim: int,
        heads: int = 8,
        dim_head: int = 64,
        dropout: float = 0.0,
        bias: bool = False,
        added_kv_proj_dim: int | None = None,
        added_proj_bias: bool | None = True,
        out_bias: bool = True,
        eps: float = 1e-5,
        out_dim: int = None,
        context_pre_only: bool | None = None,
        pre_only: bool = False,
        elementwise_affine: bool = True,
        processor=None,
    ):
        super().__init__()

        self.head_dim = dim_head
        self.inner_dim = out_dim if out_dim is not None else dim_head * heads
        self.query_dim = query_dim
        self.use_bias = bias
        self.dropout = dropout
        self.out_dim = out_dim if out_dim is not None else query_dim
        self.context_pre_only = context_pre_only
        self.pre_only = pre_only
        self.heads = out_dim // dim_head if out_dim is not None else heads
        self.added_kv_proj_dim = added_kv_proj_dim
        self.added_proj_bias = added_proj_bias

        self.norm_q = torch.nn.RMSNorm(dim_head, eps=eps, elementwise_affine=elementwise_affine)
        self.norm_k = torch.nn.RMSNorm(dim_head, eps=eps, elementwise_affine=elementwise_affine)
        self.to_q = torch.nn.Linear(query_dim, self.inner_dim, bias=bias)
        self.to_k = torch.nn.Linear(query_dim, self.inner_dim, bias=bias)
        self.to_v = torch.nn.Linear(query_dim, self.inner_dim, bias=bias)

        if not self.pre_only:
            self.to_out = torch.nn.ModuleList([])
            self.to_out.append(torch.nn.Linear(self.inner_dim, self.out_dim, bias=out_bias))
            self.to_out.append(torch.nn.Dropout(dropout))

        if added_kv_proj_dim is not None:
            self.norm_added_q = torch.nn.RMSNorm(dim_head, eps=eps)
            self.norm_added_k = torch.nn.RMSNorm(dim_head, eps=eps)
            self.add_q_proj = torch.nn.Linear(added_kv_proj_dim, self.inner_dim, bias=added_proj_bias)
            self.add_k_proj = torch.nn.Linear(added_kv_proj_dim, self.inner_dim, bias=added_proj_bias)
            self.add_v_proj = torch.nn.Linear(added_kv_proj_dim, self.inner_dim, bias=added_proj_bias)
            self.to_add_out = torch.nn.Linear(self.inner_dim, query_dim, bias=out_bias)

        if processor is None:
            processor = self._default_processor_cls()
        self.set_processor(processor)

    def forward(
        self,
        hidden_states: torch.Tensor,
        encoder_hidden_states: torch.Tensor | None = None,
        attention_mask: torch.Tensor | None = None,
        image_rotary_emb: torch.Tensor | None = None,
        **kwargs,
    ) -> torch.Tensor:
        attn_parameters = set(inspect.signature(self.processor.__call__).parameters.keys())
        quiet_attn_parameters = {"ip_adapter_masks", "ip_hidden_states"}
        unused_kwargs = [k for k, _ in kwargs.items() if k not in attn_parameters and k not in quiet_attn_parameters]
        if len(unused_kwargs) > 0:
            logger.warning(
                f"attention_kwargs {unused_kwargs} are not expected by {self.processor.__class__.__name__} and will be ignored."
            )
        kwargs = {k: w for k, w in kwargs.items() if k in attn_parameters}
        return self.processor(self, hidden_states, encoder_hidden_states, attention_mask, image_rotary_emb, **kwargs)


class BriaEmbedND(torch.nn.Module):
    # modified from https://github.com/black-forest-labs/flux/blob/c00d7c60b085fce8058b9df845e036090873f2ce/src/flux/modules/layers.py#L11
    def __init__(self, theta: int, axes_dim: list[int]):
        super().__init__()
        self.theta = theta
        self.axes_dim = axes_dim

    def forward(self, ids: torch.Tensor) -> torch.Tensor:
        n_axes = ids.shape[-1]
        cos_out = []
        sin_out = []
        pos = ids.float()
        freqs_dtype = maybe_adjust_dtype_for_device(torch.float64, ids.device)
        for i in range(n_axes):
            cos, sin = get_1d_rotary_pos_embed(
                self.axes_dim[i],
                pos[:, i],
                theta=self.theta,
                repeat_interleave_real=True,
                use_real=True,
                freqs_dtype=freqs_dtype,
            )
            cos_out.append(cos)
            sin_out.append(sin)
        freqs_cos = torch.cat(cos_out, dim=-1).to(ids.device)
        freqs_sin = torch.cat(sin_out, dim=-1).to(ids.device)
        return freqs_cos, freqs_sin


class BriaTimesteps(nn.Module):
    def __init__(
        self, num_channels: int, flip_sin_to_cos: bool, downscale_freq_shift: float, scale: int = 1, time_theta=10000
    ):
        super().__init__()
        self.num_channels = num_channels
        self.flip_sin_to_cos = flip_sin_to_cos
        self.downscale_freq_shift = downscale_freq_shift
        self.scale = scale
        self.time_theta = time_theta

    def forward(self, timesteps):
        t_emb = get_timestep_embedding(
            timesteps,
            self.num_channels,
            flip_sin_to_cos=self.flip_sin_to_cos,
            downscale_freq_shift=self.downscale_freq_shift,
            scale=self.scale,
            max_period=self.time_theta,
        )
        return t_emb


class BriaTimestepProjEmbeddings(nn.Module):
    def __init__(self, embedding_dim, time_theta):
        super().__init__()

        self.time_proj = BriaTimesteps(
            num_channels=256, flip_sin_to_cos=True, downscale_freq_shift=0, time_theta=time_theta
        )
        self.timestep_embedder = TimestepEmbedding(in_channels=256, time_embed_dim=embedding_dim)

    def forward(self, timestep, dtype):
        timesteps_proj = self.time_proj(timestep)
        timesteps_emb = self.timestep_embedder(timesteps_proj.to(dtype=dtype))  # (N, D)
        return timesteps_emb


class BriaPosEmbed(torch.nn.Module):
    # modified from https://github.com/black-forest-labs/flux/blob/c00d7c60b085fce8058b9df845e036090873f2ce/src/flux/modules/layers.py#L11
    def __init__(self, theta: int, axes_dim: list[int]):
        super().__init__()
        self.theta = theta
        self.axes_dim = axes_dim

    def forward(self, ids: torch.Tensor) -> torch.Tensor:
        n_axes = ids.shape[-1]
        cos_out = []
        sin_out = []
        pos = ids.float()
        freqs_dtype = maybe_adjust_dtype_for_device(torch.float64, ids.device)
        for i in range(n_axes):
            cos, sin = get_1d_rotary_pos_embed(
                self.axes_dim[i],
                pos[:, i],
                theta=self.theta,
                repeat_interleave_real=True,
                use_real=True,
                freqs_dtype=freqs_dtype,
            )
            cos_out.append(cos)
            sin_out.append(sin)
        freqs_cos = torch.cat(cos_out, dim=-1).to(ids.device)
        freqs_sin = torch.cat(sin_out, dim=-1).to(ids.device)
        return freqs_cos, freqs_sin


@maybe_allow_in_graph
class BriaTransformerBlock(nn.Module):
    def __init__(
        self, dim: int, num_attention_heads: int, attention_head_dim: int, qk_norm: str = "rms_norm", eps: float = 1e-6
    ):
        super().__init__()

        self.norm1 = AdaLayerNormZero(dim)
        self.norm1_context = AdaLayerNormZero(dim)

        self.attn = BriaAttention(
            query_dim=dim,
            added_kv_proj_dim=dim,
            dim_head=attention_head_dim,
            heads=num_attention_heads,
            out_dim=dim,
            context_pre_only=False,
            bias=True,
            processor=BriaAttnProcessor(),
            eps=eps,
        )

        self.norm2 = nn.LayerNorm(dim, elementwise_affine=False, eps=1e-6)
        self.ff = FeedForward(dim=dim, dim_out=dim, activation_fn="gelu-approximate")

        self.norm2_context = nn.LayerNorm(dim, elementwise_affine=False, eps=1e-6)
        self.ff_context = FeedForward(dim=dim, dim_out=dim, activation_fn="gelu-approximate")

    def forward(
        self,
        hidden_states: torch.Tensor,
        encoder_hidden_states: torch.Tensor,
        temb: torch.Tensor,
        image_rotary_emb: tuple[torch.Tensor, torch.Tensor] | None = None,
        attention_kwargs: dict[str, Any] | None = None,
    ) -> tuple[torch.Tensor, torch.Tensor]:
        norm_hidden_states, gate_msa, shift_mlp, scale_mlp, gate_mlp = self.norm1(hidden_states, emb=temb)

        norm_encoder_hidden_states, c_gate_msa, c_shift_mlp, c_scale_mlp, c_gate_mlp = self.norm1_context(
            encoder_hidden_states, emb=temb
        )
        attention_kwargs = attention_kwargs or {}

        # Attention.
        attention_outputs = self.attn(
            hidden_states=norm_hidden_states,
            encoder_hidden_states=norm_encoder_hidden_states,
            image_rotary_emb=image_rotary_emb,
            **attention_kwargs,
        )

        if len(attention_outputs) == 2:
            attn_output, context_attn_output = attention_outputs
        elif len(attention_outputs) == 3:
            attn_output, context_attn_output, ip_attn_output = attention_outputs

        # Process attention outputs for the `hidden_states`.
        attn_output = gate_msa.unsqueeze(1) * attn_output
        hidden_states = hidden_states + attn_output

        norm_hidden_states = self.norm2(hidden_states)
        norm_hidden_states = norm_hidden_states * (1 + scale_mlp[:, None]) + shift_mlp[:, None]

        ff_output = self.ff(norm_hidden_states)
        ff_output = gate_mlp.unsqueeze(1) * ff_output

        hidden_states = hidden_states + ff_output
        if len(attention_outputs) == 3:
            hidden_states = hidden_states + ip_attn_output

        # Process attention outputs for the `encoder_hidden_states`.
        context_attn_output = c_gate_msa.unsqueeze(1) * context_attn_output
        encoder_hidden_states = encoder_hidden_states + context_attn_output

        norm_encoder_hidden_states = self.norm2_context(encoder_hidden_states)
        norm_encoder_hidden_states = norm_encoder_hidden_states * (1 + c_scale_mlp[:, None]) + c_shift_mlp[:, None]

        context_ff_output = self.ff_context(norm_encoder_hidden_states)
        encoder_hidden_states = encoder_hidden_states + c_gate_mlp.unsqueeze(1) * context_ff_output
        if encoder_hidden_states.dtype == torch.float16:
            encoder_hidden_states = encoder_hidden_states.clip(-65504, 65504)

        return encoder_hidden_states, hidden_states


@maybe_allow_in_graph
class BriaSingleTransformerBlock(nn.Module):
    def __init__(self, dim: int, num_attention_heads: int, attention_head_dim: int, mlp_ratio: float = 4.0):
        super().__init__()
        self.mlp_hidden_dim = int(dim * mlp_ratio)

        self.norm = AdaLayerNormZeroSingle(dim)
        self.proj_mlp = nn.Linear(dim, self.mlp_hidden_dim)
        self.act_mlp = nn.GELU(approximate="tanh")
        self.proj_out = nn.Linear(dim + self.mlp_hidden_dim, dim)

        processor = BriaAttnProcessor()

        self.attn = BriaAttention(
            query_dim=dim,
            dim_head=attention_head_dim,
            heads=num_attention_heads,
            out_dim=dim,
            bias=True,
            processor=processor,
            eps=1e-6,
            pre_only=True,
        )

    def forward(
        self,
        hidden_states: torch.Tensor,
        encoder_hidden_states: torch.Tensor,
        temb: torch.Tensor,
        image_rotary_emb: tuple[torch.Tensor, torch.Tensor] | None = None,
        attention_kwargs: dict[str, Any] | None = None,
    ) -> tuple[torch.Tensor, torch.Tensor]:
        text_seq_len = encoder_hidden_states.shape[1]
        hidden_states = torch.cat([encoder_hidden_states, hidden_states], dim=1)

        residual = hidden_states
        norm_hidden_states, gate = self.norm(hidden_states, emb=temb)
        mlp_hidden_states = self.act_mlp(self.proj_mlp(norm_hidden_states))
        attention_kwargs = attention_kwargs or {}
        attn_output = self.attn(
            hidden_states=norm_hidden_states,
            image_rotary_emb=image_rotary_emb,
            **attention_kwargs,
        )

        hidden_states = torch.cat([attn_output, mlp_hidden_states], dim=2)
        gate = gate.unsqueeze(1)
        hidden_states = gate * self.proj_out(hidden_states)
        hidden_states = residual + hidden_states
        if hidden_states.dtype == torch.float16:
            hidden_states = hidden_states.clip(-65504, 65504)

        encoder_hidden_states, hidden_states = hidden_states[:, :text_seq_len], hidden_states[:, text_seq_len:]
        return encoder_hidden_states, hidden_states


class BriaTransformer2DModel(ModelMixin, ConfigMixin, PeftAdapterMixin, FromOriginalModelMixin, CacheMixin):
    """
    The Transformer model introduced in Flux. Based on FluxPipeline with several changes:
    - no pooled embeddings
    - We use zero padding for prompts
    - No guidance embedding since this is not a distilled version
    Reference: https://blackforestlabs.ai/announcing-black-forest-labs/

    Parameters:
        patch_size (`int`): Patch size to turn the input data into small patches.
        in_channels (`int`, *optional*, defaults to 16): The number of channels in the input.
        num_layers (`int`, *optional*, defaults to 18): The number of layers of MMDiT blocks to use.
        num_single_layers (`int`, *optional*, defaults to 18): The number of layers of single DiT blocks to use.
        attention_head_dim (`int`, *optional*, defaults to 64): The number of channels in each head.
        num_attention_heads (`int`, *optional*, defaults to 18): The number of heads to use for multi-head attention.
        joint_attention_dim (`int`, *optional*): The number of `encoder_hidden_states` dimensions to use.
        pooled_projection_dim (`int`): Number of dimensions to use when projecting the `pooled_projections`.
        guidance_embeds (`bool`, defaults to False): Whether to use guidance embeddings.
    """

    _supports_gradient_checkpointing = True

    @register_to_config
    def __init__(
        self,
        patch_size: int = 1,
        in_channels: int = 64,
        num_layers: int = 19,
        num_single_layers: int = 38,
        attention_head_dim: int = 128,
        num_attention_heads: int = 24,
        joint_attention_dim: int = 4096,
        pooled_projection_dim: int = None,
        guidance_embeds: bool = False,
        axes_dims_rope: list[int] = [16, 56, 56],
        rope_theta=10000,
        time_theta=10000,
    ):
        super().__init__()
        self.out_channels = in_channels
        self.inner_dim = self.config.num_attention_heads * self.config.attention_head_dim

        self.pos_embed = BriaEmbedND(theta=rope_theta, axes_dim=axes_dims_rope)

        self.time_embed = BriaTimestepProjEmbeddings(embedding_dim=self.inner_dim, time_theta=time_theta)
        if guidance_embeds:
            self.guidance_embed = BriaTimestepProjEmbeddings(embedding_dim=self.inner_dim)

        self.context_embedder = nn.Linear(self.config.joint_attention_dim, self.inner_dim)
        self.x_embedder = torch.nn.Linear(self.config.in_channels, self.inner_dim)

        self.transformer_blocks = nn.ModuleList(
            [
                BriaTransformerBlock(
                    dim=self.inner_dim,
                    num_attention_heads=self.config.num_attention_heads,
                    attention_head_dim=self.config.attention_head_dim,
                )
                for i in range(self.config.num_layers)
            ]
        )

        self.single_transformer_blocks = nn.ModuleList(
            [
                BriaSingleTransformerBlock(
                    dim=self.inner_dim,
                    num_attention_heads=self.config.num_attention_heads,
                    attention_head_dim=self.config.attention_head_dim,
                )
                for i in range(self.config.num_single_layers)
            ]
        )

        self.norm_out = AdaLayerNormContinuous(self.inner_dim, self.inner_dim, elementwise_affine=False, eps=1e-6)
        self.proj_out = nn.Linear(self.inner_dim, patch_size * patch_size * self.out_channels, bias=True)

        self.gradient_checkpointing = False

    @apply_lora_scale("attention_kwargs")
    def forward(
        self,
        hidden_states: torch.Tensor,
        encoder_hidden_states: torch.Tensor = None,
        pooled_projections: torch.Tensor = None,
        timestep: torch.LongTensor = None,
        img_ids: torch.Tensor = None,
        txt_ids: torch.Tensor = None,
        guidance: torch.Tensor = None,
        attention_kwargs: dict[str, Any] | None = None,
        return_dict: bool = True,
        controlnet_block_samples=None,
        controlnet_single_block_samples=None,
    ) -> tuple[torch.Tensor] | Transformer2DModelOutput:
        """
        The [`BriaTransformer2DModel`] forward method.

        Args:
            hidden_states (`torch.FloatTensor` of shape `(batch size, channel, height, width)`):
                Input `hidden_states`.
            encoder_hidden_states (`torch.FloatTensor` of shape `(batch size, sequence_len, embed_dims)`):
                Conditional embeddings (embeddings computed from the input conditions such as prompts) to use.
            pooled_projections (`torch.FloatTensor` of shape `(batch_size, projection_dim)`): Embeddings projected
                from the embeddings of input conditions.
            timestep ( `torch.LongTensor`):
                Used to indicate denoising step.
            img_ids (`torch.Tensor`):
                Image position ids used to compute the rotary positional embeddings.
            txt_ids (`torch.Tensor`):
                Text position ids used to compute the rotary positional embeddings.
            guidance (`torch.Tensor`, *optional*):
                Guidance scale embedding used for guidance-distilled variants of the model.
            controlnet_block_samples (`list` of `torch.Tensor`, *optional*):
                A list of tensors that if specified are added to the residuals of transformer blocks.
            controlnet_single_block_samples (`list` of `torch.Tensor`, *optional*):
                A list of tensors that if specified are added to the residuals of single transformer blocks.
            attention_kwargs (`dict`, *optional*):
                A kwargs dictionary that if specified is passed along to the `AttentionProcessor` as defined under
                `self.processor` in
                [diffusers.models.attention_processor](https://github.com/huggingface/diffusers/blob/main/src/diffusers/models/attention_processor.py).
            return_dict (`bool`, *optional*, defaults to `True`):
                Whether or not to return a [`~models.transformer_2d.Transformer2DModelOutput`] instead of a plain
                tuple.

        Returns:
            If `return_dict` is True, an [`~models.transformer_2d.Transformer2DModelOutput`] is returned, otherwise a
            `tuple` where the first element is the sample tensor.
        """
        hidden_states = self.x_embedder(hidden_states)

        timestep = timestep.to(hidden_states.dtype)
        if guidance is not None:
            guidance = guidance.to(hidden_states.dtype)
        else:
            guidance = None

        temb = self.time_embed(timestep, dtype=hidden_states.dtype)

        if guidance:
            temb += self.guidance_embed(guidance, dtype=hidden_states.dtype)

        encoder_hidden_states = self.context_embedder(encoder_hidden_states)

        if len(txt_ids.shape) == 3:
            txt_ids = txt_ids[0]

        if len(img_ids.shape) == 3:
            img_ids = img_ids[0]

        ids = torch.cat((txt_ids, img_ids), dim=0)
        image_rotary_emb = self.pos_embed(ids)

        for index_block, block in enumerate(self.transformer_blocks):
            if torch.is_grad_enabled() and self.gradient_checkpointing:
                encoder_hidden_states, hidden_states = self._gradient_checkpointing_func(
                    block,
                    hidden_states,
                    encoder_hidden_states,
                    temb,
                    image_rotary_emb,
                    attention_kwargs,
                )

            else:
                encoder_hidden_states, hidden_states = block(
                    hidden_states=hidden_states,
                    encoder_hidden_states=encoder_hidden_states,
                    temb=temb,
                    image_rotary_emb=image_rotary_emb,
                )

            # controlnet residual
            if controlnet_block_samples is not None:
                interval_control = len(self.transformer_blocks) / len(controlnet_block_samples)
                interval_control = int(np.ceil(interval_control))
                hidden_states = hidden_states + controlnet_block_samples[index_block // interval_control]

        for index_block, block in enumerate(self.single_transformer_blocks):
            if torch.is_grad_enabled() and self.gradient_checkpointing:
                encoder_hidden_states, hidden_states = self._gradient_checkpointing_func(
                    block,
                    hidden_states,
                    encoder_hidden_states,
                    temb,
                    image_rotary_emb,
                    attention_kwargs,
                )

            else:
                encoder_hidden_states, hidden_states = block(
                    hidden_states=hidden_states,
                    encoder_hidden_states=encoder_hidden_states,
                    temb=temb,
                    image_rotary_emb=image_rotary_emb,
                )

            # controlnet residual
            if controlnet_single_block_samples is not None:
                interval_control = len(self.single_transformer_blocks) / len(controlnet_single_block_samples)
                interval_control = int(np.ceil(interval_control))
                hidden_states[:, encoder_hidden_states.shape[1] :, ...] = (
                    hidden_states[:, encoder_hidden_states.shape[1] :, ...]
                    + controlnet_single_block_samples[index_block // interval_control]
                )

        hidden_states = self.norm_out(hidden_states, temb)
        output = self.proj_out(hidden_states)

        if not return_dict:
            return (output,)

        return Transformer2DModelOutput(sample=output)