torch/ao/quantization/quantize_fx.py

from typing import Any, Dict, Optional, Set, Tuple, Union
import warnings

import torch
from torch.fx import GraphModule
from .fx.tracer import QuantizationTracer
from .fx import fuse  # noqa: F401
from .fx import prepare  # noqa: F401
from .fx.convert import convert
from .backend_config import (  # noqa: F401
    BackendConfig,
    get_tensorrt_backend_config,
)
from .fx.graph_module import ObservedGraphModule
from .fx.custom_config import (
    ConvertCustomConfig,
    FuseCustomConfig,
    PrepareCustomConfig,
)
from .fx.utils import graph_pretty_str  # noqa: F401
from .fx.utils import get_custom_module_class_keys  # noqa: F401
from .fx.utils import get_skipped_module_name_and_classes
from .qconfig_mapping import QConfigMapping

def _check_is_graph_module(model: torch.nn.Module) -> None:
    if not isinstance(model, GraphModule):
        raise ValueError(
            "input model must be a GraphModule, "
            + "Got type:"
            + str(type(model))
            + " Please make "
            + "sure to follow the tutorials."
        )


def _swap_ff_with_fxff(model: torch.nn.Module) -> None:
    r""" Swap FloatFunctional with FXFloatFunctional
    """
    modules_to_swap = []
    for name, module in model.named_children():
        if isinstance(module, torch.ao.nn.quantized.FloatFunctional):
            modules_to_swap.append(name)
        else:
            _swap_ff_with_fxff(module)

    for name in modules_to_swap:
        del model._modules[name]
        model._modules[name] = torch.ao.nn.quantized.FXFloatFunctional()


def _fuse_fx(
    graph_module: GraphModule,
    is_qat: bool,
    fuse_custom_config: Union[FuseCustomConfig, Dict[str, Any], None] = None,
    backend_config: Union[BackendConfig, Dict[str, Any], None] = None,
) -> GraphModule:
    r""" Internal helper function to fuse modules in preparation for quantization

    Args:
        graph_module: GraphModule object from symbolic tracing (torch.fx.symbolic_trace)
    """
    _check_is_graph_module(graph_module)
    return fuse(
        graph_module, is_qat, fuse_custom_config, backend_config)  # type: ignore[operator]


class Scope(object):
    """ Scope object that records the module path and the module type
    of a module. Scope is used to track the information of the module
    that contains a Node in a Graph of GraphModule. For example::

        class Sub(torch.nn.Module):
            def forward(self, x):
                # This will be a call_method Node in GraphModule,
                # scope for this would be (module_path="sub", module_type=Sub)
                return x.transpose(1, 2)

        class M(torch.nn.Module):
            def __init__(self):
                self.sub = Sub()

            def forward(self, x):
                # This will be a call_method Node as well,
                # scope for this would be (module_path="", None)
                x = x.transpose(1, 2)
                x = self.sub(x)
                return x

    """

    def __init__(self, module_path: str, module_type: Any):
        super().__init__()
        self.module_path = module_path
        self.module_type = module_type


class ScopeContextManager(object):
    """ A context manager to track the Scope of Node during symbolic tracing.
    When entering a forward function of a Module, we'll update the scope information of
    the current module, and when we exit, we'll restore the previous scope information.
    """

    def __init__(
        self, scope: Scope, current_module: torch.nn.Module, current_module_path: str
    ):
        super().__init__()
        self.prev_module_type = scope.module_type
        self.prev_module_path = scope.module_path
        self.scope = scope
        self.scope.module_path = current_module_path
        self.scope.module_type = type(current_module)

    def __enter__(self):
        return

    def __exit__(self, *args):
        self.scope.module_path = self.prev_module_path
        self.scope.module_type = self.prev_module_type
        return


def _prepare_fx(
    model: torch.nn.Module,
    qconfig_mapping: Union[QConfigMapping, Dict[str, Any]],
    is_qat: bool,
    example_inputs: Tuple[Any, ...],
    prepare_custom_config: Union[PrepareCustomConfig, Dict[str, Any], None] = None,
    _equalization_config: Optional[Union[QConfigMapping, Dict[str, Any]]] = None,
    backend_config: Union[BackendConfig, Dict[str, Any], None] = None,
    is_standalone_module: bool = False,
) -> ObservedGraphModule:
    r""" Internal helper function for prepare_fx
    Args:
      `model`, `qconfig_mapping`, `prepare_custom_config`, `_equalization_config`:
      see docs for :func:`~torch.ao.quantization.prepare_fx`
      `is_standalone_module`: a boolean flag indicates whether we are
      quantizing a standalone module or not, a standalone module
      is a submodule of the parent module that is not inlined in the
forward graph of the parent module,
      the way we quantize standalone module is described in:
      :func:`~torch.ao.quantization._prepare_standalone_module_fx`
    """
    if prepare_custom_config is None:
        prepare_custom_config = PrepareCustomConfig()
    if _equalization_config is None:
        _equalization_config = QConfigMapping()

    if isinstance(prepare_custom_config, Dict):
        warnings.warn(
            "Passing a prepare_custom_config_dict to prepare is deprecated and will not be supported "
            "in a future version. Please pass in a PrepareCustomConfig instead.")
        prepare_custom_config = PrepareCustomConfig.from_dict(prepare_custom_config)

    # swap FloatFunctional with FXFloatFunctional
    _swap_ff_with_fxff(model)

    skipped_module_names, skipped_module_classes = \
        get_skipped_module_name_and_classes(prepare_custom_config, is_standalone_module)
    preserved_attributes = prepare_custom_config.preserved_attributes
    # symbolically trace the model
    tracer = QuantizationTracer(skipped_module_names, skipped_module_classes)  # type: ignore[arg-type]
    graph_module = GraphModule(model, tracer.trace(model))
    for attr_name in preserved_attributes:
        setattr(graph_module, attr_name, getattr(model, attr_name))
    fuse_custom_config = FuseCustomConfig().set_preserved_attributes(prepare_custom_config.preserved_attributes)
    graph_module = _fuse_fx(
        graph_module,
        is_qat,
        fuse_custom_config,
        backend_config)
    prepared = prepare(
        graph_module,
        qconfig_mapping,
        is_qat,
        tracer.node_name_to_scope,
        example_inputs=example_inputs,
        prepare_custom_config=prepare_custom_config,
        _equalization_config=_equalization_config,
        backend_config=backend_config,
        is_standalone_module=is_standalone_module,
    )  # type: ignore[operator]

    for attr_name in preserved_attributes:
        setattr(prepared, attr_name, getattr(model, attr_name))
    return prepared


def _prepare_standalone_module_fx(
    model: torch.nn.Module,
    qconfig_mapping: Union[QConfigMapping, Dict[str, Any]],
    is_qat: bool,
    example_inputs: Tuple[Any, ...],
    prepare_custom_config: Union[PrepareCustomConfig, Dict[str, Any], None] = None,
    backend_config: Union[BackendConfig, Dict[str, Any], None] = None,
) -> GraphModule:
    r""" [Internal use only] Prepare a standalone module, so that it can be used when quantizing the
    parent module.
    standalone_module means it a submodule that is not inlined in parent module,
    and will be quantized separately as one unit.

    How the standalone module is observed is specified by `input_quantized_idxs` and
    `output_quantized_idxs` in the prepare_custom_config for the standalone module

    Returns:

        * model(GraphModule): prepared standalone module. It has these attributes:

            * `_standalone_module_input_quantized_idxs(List[Int])`: a list of
              indexes for the graph input that is expected to be quantized,
              same as input_quantized_idxs configuration provided
              for the standalone module
            * `_standalone_module_output_quantized_idxs(List[Int])`: a list of
              indexs for the graph output that is quantized
              same as input_quantized_idxs configuration provided
              for the standalone module

    """
    return _prepare_fx(
        model,
        qconfig_mapping,
        is_qat,
        example_inputs,
        prepare_custom_config,
        backend_config=backend_config,
        is_standalone_module=True,
    )


def fuse_fx(
    model: torch.nn.Module,
    fuse_custom_config: Union[FuseCustomConfig, Dict[str, Any], None] = None,
    backend_config: Union[BackendConfig, Dict[str, Any], None] = None,
) -> GraphModule:
    r""" Fuse modules like conv+bn, conv+bn+relu etc, model must be in eval mode.
    Fusion rules are defined in torch.quantization.fx.fusion_pattern.py

    Args:

        * `model` (torch.nn.Module): a torch.nn.Module model
        * `fuse_custom_config` (FuseCustomConfig): custom configurations for fuse_fx.
            See :class:`~torch.ao.quantization.fx.custom_config.FuseCustomConfig` for more details
    Example::

        from torch.ao.quantization import fuse_fx
        m = Model().eval()
        m = fuse_fx(m)

    """
    if fuse_custom_config is None:
        fuse_custom_config = FuseCustomConfig()

    if isinstance(fuse_custom_config, Dict):
        warnings.warn(
            "Passing a fuse_custom_config_dict to fuse is deprecated and will not be supported "
            "in a future version. Please pass in a FuseCustomConfig instead.")
        fuse_custom_config = FuseCustomConfig.from_dict(fuse_custom_config)

    torch._C._log_api_usage_once("quantization_api.quantize_fx.fuse_fx")
    graph_module = torch.fx.symbolic_trace(model)
    preserved_attributes: Set[str] = set()
    if fuse_custom_config:
        preserved_attributes = set(fuse_custom_config.preserved_attributes)
    for attr_name in preserved_attributes:
        setattr(graph_module, attr_name, getattr(model, attr_name))
    return _fuse_fx(graph_module, False, fuse_custom_config, backend_config)


def prepare_fx(
    model: torch.nn.Module,
    qconfig_mapping: Union[QConfigMapping, Dict[str, Any]],
    example_inputs: Tuple[Any, ...],
    prepare_custom_config: Union[PrepareCustomConfig, Dict[str, Any], None] = None,
    _equalization_config: Optional[Union[QConfigMapping, Dict[str, Any]]] = None,
    backend_config: Union[BackendConfig, Dict[str, Any], None] = None,
) -> ObservedGraphModule:
    r""" Prepare a model for post training static quantization

    Args:
      * `model` (torch.nn.Module): torch.nn.Module model

      * `qconfig_mapping` (QConfigMapping): QConfigMapping object to configure how a model is
         quantized, see :class:`~torch.ao.quantization.qconfig_mapping.QConfigMapping`
         for more details

      * `example_inputs` (Tuple[Any, ...]): Example inputs for forward function of the model,
         Tuple of positional args (keyword args can be passed as positional args as well)

      * `prepare_custom_config` (PrepareCustomConfig): customization configuration for quantization tool.
          See :class:`~torch.ao.quantization.fx.custom_config.PrepareCustomConfig` for more details

      * `_equalization_config`: config for specifying how to perform equalization on the model

      * `backend_config` (BackendConfig): config that specifies how operators are quantized
         in a backend, this includes how the operaetors are observed,
         supported fusion patterns, how quantize/dequantize ops are
         inserted, supported dtypes etc. See :class:`~torch.ao.quantization.backend_config.BackendConfig` for more details

    Return:
      A GraphModule with observer (configured by qconfig_mapping), ready for calibration

    Example::

        import torch
        from torch.ao.quantization import get_default_qconfig_mapping
        from torch.ao.quantization import prepare_fx

        class Submodule(torch.nn.Module):
            def __init__(self):
                super().__init__()
                self.linear = torch.nn.Linear(5, 5)
            def forward(self, x):
                x = self.linear(x)
                return x

        class M(torch.nn.Module):
            def __init__(self):
                super().__init__()
                self.linear = torch.nn.Linear(5, 5)
                self.sub = Submodule()

            def forward(self, x):
                x = self.linear(x)
                x = self.sub(x) + x
                return x

        # initialize a floating point model
        float_model = M().eval()

        # define calibration function
        def calibrate(model, data_loader):
            model.eval()
            with torch.no_grad():
                for image, target in data_loader:
                    model(image)

        # qconfig is the configuration for how we insert observers for a particular
        # operator
        # qconfig = get_default_qconfig("fbgemm")
        # Example of customizing qconfig:
        # qconfig = torch.ao.quantization.QConfig(
        #    activation=MinMaxObserver.with_args(dtype=torch.qint8),
        #    weight=MinMaxObserver.with_args(dtype=torch.qint8))
        # `activation` and `weight` are constructors of observer module

        # qconfig_mapping is a collection of quantization configurations, user can
        # set the qconfig for each operator (torch op calls, functional calls, module calls)
        # in the model through qconfig_mapping
        # the following call will get the qconfig_mapping that works best for models
        # that target "fbgemm" backend
        qconfig_mapping = get_default_qconfig_mapping("fbgemm")

        # We can customize qconfig_mapping in different ways.
        # e.g. set the global qconfig, which means we will use the same qconfig for
        # all operators in the model, this can be overwritten by other settings
        # qconfig_mapping = QConfigMapping().set_global(qconfig)
        # e.g. quantize the linear submodule with a specific qconfig
        # qconfig_mapping = QConfigMapping().set_module_name("linear", qconfig)
        # e.g. quantize all nn.Linear modules with a specific qconfig
        # qconfig_mapping = QConfigMapping().set_object_type(torch.nn.Linear, qconfig)
        # for a more complete list, please see the docstring for :class:`torch.ao.quantization.QConfigMapping`
        # argument

        # example_inputs is a tuple of inputs, that is used to infer the type of the
        # outputs in the model
        # currently it's not used, but please make sure model(*example_inputs) runs
        example_inputs = (torch.randn(1, 3, 224, 224),)

        # TODO: add backend_config after we split the backend_config for fbgemm and qnnpack
        # e.g. backend_config = get_default_backend_config("fbgemm")
        # `prepare_fx` inserts observers in the model based on qconfig_mapping and
        # backend_config. If the configuration for an operator in qconfig_mapping
        # is supported in the backend_config (meaning it's supported by the target
        # hardware), we'll insert observer modules according to the qconfig_mapping
        # otherwise the configuration in qconfig_mapping will be ignored
        #
        # Example:
        # in qconfig_mapping, user sets linear module to be quantized with quint8 for
        # activation and qint8 for weight:
        # qconfig = torch.ao.quantization.QConfig(
        #     observer=MinMaxObserver.with_args(dtype=torch.quint8),
        #     weight=MinMaxObserver.with-args(dtype=torch.qint8))
        # Note: current qconfig api does not support setting output observer, but
        # we may extend this to support these more fine grained control in the
        # future
        #
        # qconfig_mapping = QConfigMapping().set_object_type(torch.nn.Linear, qconfig)
        # in backend config, linear module also supports in this configuration:
        # weighted_int8_dtype_config = DTypeConfig(
        #   input_dtype=torch.quint8,
        #   output_dtype=torch.quint8,
        #   weight_dtype=torch.qint8,
        #   bias_type=torch.float)

        # linear_pattern_config = BackendPatternConfig(torch.nn.Linear) \
        #    .set_observation_type(ObservationType.OUTPUT_USE_DIFFERENT_OBSERVER_AS_INPUT) \
        #    .add_dtype_config(weighted_int8_dtype_config) \
        #    ...

        # backend_config = BackendConfig().set_backend_pattern_config(linear_pattern_config)
        # `prepare_fx` will check that the setting requested by suer in qconfig_mapping
        # is supported by the backend_config and insert observers and fake quant modules
        # in the model
        prepared_model = prepare_fx(float_model, qconfig_mapping, example_inputs)
        # Run calibration
        calibrate(prepared_model, sample_inference_data)
    """
    torch._C._log_api_usage_once("quantization_api.quantize_fx.prepare_fx")
    return _prepare_fx(
        model,
        qconfig_mapping,
        False,  # is_qat
        example_inputs,
        prepare_custom_config,
        _equalization_config,
        backend_config,
    )


def prepare_qat_fx(
    model: torch.nn.Module,
    qconfig_mapping: Union[QConfigMapping, Dict[str, Any]],
    example_inputs: Tuple[Any, ...],
    prepare_custom_config: Union[PrepareCustomConfig, Dict[str, Any], None] = None,
    backend_config: Union[BackendConfig, Dict[str, Any], None] = None,
) -> ObservedGraphModule:
    r""" Prepare a model for quantization aware training

    Args:
      * `model` (torch.nn.Module): torch.nn.Module model
      * `qconfig_mapping` (QConfigMapping): see :func:`~torch.ao.quantization.prepare_fx`
      * `example_inputs` (Tuple[Any, ...]): see :func:`~torch.ao.quantization.prepare_fx`
      * `prepare_custom_config` (PrepareCustomConfig): see :func:`~torch.ao.quantization.prepare_fx`
      * `backend_config` (BackendConfig): see :func:`~torch.ao.quantization.prepare_fx`

    Return:
      A GraphModule with fake quant modules (configured by qconfig_mapping and backend_config), ready for
      quantization aware training

    Example::

        import torch
        from torch.ao.quantization import get_default_qat_qconfig_mapping
        from torch.ao.quantization import prepare_fx

        class Submodule(torch.nn.Module):
            def __init__(self):
                super().__init__()
                self.linear = torch.nn.Linear(5, 5)
            def forward(self, x):
                x = self.linear(x)
                return x

        class M(torch.nn.Module):
            def __init__(self):
                super().__init__()
                self.linear = torch.nn.Linear(5, 5)
                self.sub = Submodule()

            def forward(self, x):
                x = self.linear(x)
                x = self.sub(x) + x
                return x

        # initialize a floating point model
        float_model = M().train()
        # (optional, but preferred) load the weights from pretrained model
        # float_model.load_weights(...)

        # define the training loop for quantization aware training
        def train_loop(model, train_data):
            model.train()
            for image, target in data_loader:
                ...

        # qconfig is the configuration for how we insert observers for a particular
        # operator
        # qconfig = get_default_qconfig("fbgemm")
        # Example of customizing qconfig:
        # qconfig = torch.ao.quantization.QConfig(
        #    activation=FakeQuantize.with_args(observer=MinMaxObserver.with_args(dtype=torch.qint8)),
        #    weight=FakeQuantize.with_args(observer=MinMaxObserver.with_args(dtype=torch.qint8)))
        # `activation` and `weight` are constructors of observer module

        # qconfig_mapping is a collection of quantization configurations, user can
        # set the qconfig for each operator (torch op calls, functional calls, module calls)
        # in the model through qconfig_mapping
        # the following call will get the qconfig_mapping that works best for models
        # that target "fbgemm" backend
        qconfig_mapping = get_default_qat_qconfig("fbgemm")

        # We can customize qconfig_mapping in different ways, please take a look at
        # the doctring for :func:`~torch.ao.quantization.prepare_fx` for different ways
        # to configure this

        # example_inputs is a tuple of inputs, that is used to infer the type of the
        # outputs in the model
        # currently it's not used, but please make sure model(*example_inputs) runs
        example_inputs = (torch.randn(1, 3, 224, 224),)

        # TODO: add backend_config after we split the backend_config for fbgemm and qnnpack
        # e.g. backend_config = get_default_backend_config("fbgemm")
        # `prepare_qat_fx` inserts observers in the model based on qconfig_mapping and
        # backend_config, if the configuration for an operator in qconfig_mapping
        # is supported in the backend_config (meaning it's supported by the target
        # hardware), we'll insert fake_quantize modules according to the qconfig_mapping
        # otherwise the configuration in qconfig_mapping will be ignored
        # see :func:`~torch.ao.quantization.prepare_fx` for a detailed explanation of
        # how qconfig_mapping interacts with backend_config
        prepared_model = prepare_qat_fx(float_model, qconfig_mapping, example_inputs)
        # Run training
        train_loop(prepared_model, train_loop)

    """
    torch._C._log_api_usage_once("quantization_api.quantize_fx.prepare_qat_fx")
    return _prepare_fx(
        model,
        qconfig_mapping,
        True,  # is_qat
        example_inputs,
        prepare_custom_config,
        backend_config=backend_config,
    )


def _convert_fx(
    graph_module: GraphModule,
    is_reference: bool,
    convert_custom_config: Union[ConvertCustomConfig, Dict[str, Any], None] = None,
    is_standalone_module: bool = False,
    _remove_qconfig: bool = True,
    qconfig_mapping: Union[QConfigMapping, Dict[str, Any], None] = None,
    backend_config: Union[BackendConfig, Dict[str, Any], None] = None,
) -> torch.nn.Module:
    """ `is_standalone_module`: see docs in :func:`~torch.ao.quantization.prepare_standalone_module_fx`
    """
    if convert_custom_config is None:
        convert_custom_config = ConvertCustomConfig()

    if isinstance(convert_custom_config, Dict):
        warnings.warn(
            "Passing a convert_custom_config_dict to convert is deprecated and will not be supported "
            "in a future version. Please pass in a ConvertCustomConfig instead.")
        convert_custom_config = ConvertCustomConfig.from_dict(convert_custom_config)

    _check_is_graph_module(graph_module)

    quantized = convert(
        graph_module,
        is_reference,
        convert_custom_config,
        is_standalone_module,
        _remove_qconfig_flag=_remove_qconfig,
        qconfig_mapping=qconfig_mapping,
        backend_config=backend_config,
    )

    preserved_attributes = convert_custom_config.preserved_attributes
    for attr_name in preserved_attributes:
        setattr(quantized, attr_name, getattr(graph_module, attr_name))
    return quantized


def convert_fx(
    graph_module: GraphModule,
    convert_custom_config: Union[ConvertCustomConfig, Dict[str, Any], None] = None,
    _remove_qconfig: bool = True,
    qconfig_mapping: Union[QConfigMapping, Dict[str, Any], None] = None,
    backend_config: Union[BackendConfig, Dict[str, Any], None] = None,
) -> torch.nn.Module:
    r""" Convert a calibrated or trained model to a quantized model

    Args:
        * `graph_module` (torch.fx.GraphModule): A prepared and calibrated/trained model (GraphModule)

        * `convert_custom_config` (ConvertCustomConfig): custom configurations for convert function.
            See :class:`~torch.ao.quantization.fx.custom_config.ConvertCustomConfig` for more details

        * `_remove_qconfig` (bool): Option to remove the qconfig attributes in the model after convert.

        * `qconfig_mapping` (QConfigMapping): config for specifying how to convert a model for quantization.

           The keys must include the ones in the qconfig_mapping passed to `prepare_fx` or `prepare_qat_fx`,
           with the same values or `None`. Additional keys can be specified with values set to `None`.

          For each entry whose value is set to None, we skip quantizing that entry in the model::

            qconfig_mapping = QConfigMapping
                .set_global(qconfig_from_prepare)
                .set_object_type(torch.nn.functional.add, None)  # skip quantizing torch.nn.functional.add
                .set_object_type(torch.nn.functional.linear, qconfig_from_prepare)
                .set_module_name("foo.bar", None)  # skip quantizing module "foo.bar"

         * `backend_config` (BackendConfig): A configuration for the backend which describes how
            operators should be quantized in the backend, this includes quantization
            mode support (static/dynamic/weight_only), dtype support (quint8/qint8 etc.),
            observer placement for each operators and fused operators.
            See :class:`~torch.ao.quantization.backend_config.BackendConfig` for more details

    Return:
        A quantized model (torch.nn.Module)

    Example::

        # prepared_model: the model after prepare_fx/prepare_qat_fx and calibration/training
        # convert_fx converts a calibrated/trained model to a quantized model for the
        # target hardware, this includes converting the model first to a reference
        # quantized model, and then lower the reference quantized model to a backend
        # Currently, the supported backends are fbgemm (onednn), qnnpack (xnnpack) and
        # they share the same set of quantized operators, so we are using the same
        # lowering procedure
        #
        # backend_config defines the corresponding reference quantized module for
        # the weighted modules in the model, e.g. nn.Linear
        # TODO: add backend_config after we split the backend_config for fbgemm and qnnpack
        # e.g. backend_config = get_default_backend_config("fbgemm")
        quantized_model = convert_fx(prepared_model)

    """
    torch._C._log_api_usage_once("quantization_api.quantize_fx.convert_fx")
    return _convert_fx(
        graph_module,
        is_reference=False,
        convert_custom_config=convert_custom_config,
        _remove_qconfig=_remove_qconfig,
        qconfig_mapping=qconfig_mapping,
        backend_config=backend_config,
    )


def convert_to_reference_fx(
    graph_module: GraphModule,
    convert_custom_config: Union[ConvertCustomConfig, Dict[str, Any], None] = None,
    _remove_qconfig: bool = True,
    qconfig_mapping: Union[QConfigMapping, Dict[str, Any], None] = None,
    backend_config: Union[BackendConfig, Dict[str, Any], None] = None,
) -> torch.nn.Module:
    r""" Convert a calibrated or trained model to a reference quantized model,
    see https://github.com/pytorch/rfcs/blob/master/RFC-0019-Extending-PyTorch-Quantization-to-Custom-Backends.md for more details,
    reference quantzied model is a standard representation of a quantized model provided
    by FX Graph Mode Quantization, it can be further lowered to run on the target
    hardware, like accelerators

    Args:
        * `graph_module` (GraphModule): A prepared and calibrated/trained model (GraphModule)

        * `convert_custom_config` (ConvertCustomConfig): custom configurations for convert function.
            See :func:`~torch.ao.quantization.quantize_fx.convert_fx` for more details.

        * `_remove_qconfig` (bool): Option to remove the qconfig attributes in the model after convert.

        * `qconfig_mapping` (QConfigMapping): config for specifying how to convert a model for quantization.
            See :func:`~torch.ao.quantization.quantize_fx.convert_fx` for more details.

         * `backend_config` (BackendConfig): A configuration for the backend which describes how
            operators should be quantized in the backend. See
            :func:`~torch.ao.quantization.quantize_fx.convert_fx` for more details.

    Return:
        A reference quantized model (GraphModule)

    Example::

        # prepared_model: the model after prepare_fx/prepare_qat_fx and calibration/training
        # TODO: add backend_config after we split the backend_config for fbgemm and qnnpack
        # e.g. backend_config = get_default_backend_config("fbgemm")
        reference_quantized_model = convert_to_reference_fx(prepared_model)

    """
    torch._C._log_api_usage_once("quantization_api.quantize_fx.convert_to_reference_fx")
    return _convert_fx(
        graph_module,
        is_reference=True,
        convert_custom_config=convert_custom_config,
        _remove_qconfig=_remove_qconfig,
        qconfig_mapping=qconfig_mapping,
        backend_config=backend_config,
    )


def _convert_standalone_module_fx(
    graph_module: GraphModule,
    is_reference: bool = False,
    convert_custom_config: Union[ConvertCustomConfig, Dict[str, Any], None] = None,
) -> torch.nn.Module:
    r""" [Internal use only] Convert a model produced by :func:`~torch.ao.quantization.prepare_standalone_module_fx`
    and convert it to a quantized model

    Returns a quantized standalone module, whether input/output is quantized is
    specified by prepare_custom_config, with
    input_quantized_idxs, output_quantized_idxs, please
    see docs for prepare_fx for details
    """
    return _convert_fx(
        graph_module,
        is_reference,
        convert_custom_config,
        is_standalone_module=True,
    )