Return type:
      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)
