src/transformers/modeling_tf_pytorch_utils.py/load_tf2_state_dict_in_pytorch_model
def load_tf2_state_dict_in_pytorch_model(pt_model, tf_state_dict, allow_missing_keys=False, output_loading_info=False):
    import torch

    new_pt_params_dict = {}
    current_pt_params_dict = dict(pt_model.named_parameters())

    # Make sure we are able to load PyTorch base models as well as derived models (with heads)
    # TF models always have a prefix, some of PyTorch models (base ones) don't
    start_prefix_to_remove = ""
    if not any(s.startswith(pt_model.base_model_prefix) for s in current_pt_params_dict.keys()):
        start_prefix_to_remove = pt_model.base_model_prefix + "."

    # Build a map from potential PyTorch weight names to TF 2.0 Variables
    tf_weights_map = {}
    for name, tf_weight in tf_state_dict.items():
        pt_name, transpose = convert_tf_weight_name_to_pt_weight_name(
            name, start_prefix_to_remove=start_prefix_to_remove, tf_weight_shape=tf_weight.shape
        )
        tf_weights_map[pt_name] = (tf_weight, transpose)

    all_tf_weights = set(tf_weights_map.keys())
    loaded_pt_weights_data_ptr = {}
    missing_keys_pt = []
    for pt_weight_name, pt_weight in current_pt_params_dict.items():
        # Handle PyTorch shared weight ()not duplicated in TF 2.0
        if pt_weight.data_ptr() in loaded_pt_weights_data_ptr:
            new_pt_params_dict[pt_weight_name] = loaded_pt_weights_data_ptr[pt_weight.data_ptr()]
            continue

        # Find associated numpy array in pytorch model state dict
        if pt_weight_name not in tf_weights_map:
            if allow_missing_keys:
                missing_keys_pt.append(pt_weight_name)
                continue

            raise AttributeError(f"{pt_weight_name} not found in TF 2.0 model")

        array, transpose = tf_weights_map[pt_weight_name]

        array = apply_transpose(transpose, array, pt_weight.shape, pt_to_tf=False)

        if numpy.isscalar(array):
            array = numpy.array(array)
        if not is_torch_tensor(array) and not is_numpy_array(array):
            array = array.numpy()
        if is_numpy_array(array):
            # Convert to torch tensor
            array = torch.from_numpy(array)

        new_pt_params_dict[pt_weight_name] = array
        loaded_pt_weights_data_ptr[pt_weight.data_ptr()] = array
        all_tf_weights.discard(pt_weight_name)

    missing_keys, unexpected_keys = pt_model.load_state_dict(new_pt_params_dict, strict=False)
    missing_keys += missing_keys_pt

    # Some models may have keys that are not in the state by design, removing them before needlessly warning
    # the user.
    if pt_model._keys_to_ignore_on_load_missing is not None:
        for pat in pt_model._keys_to_ignore_on_load_missing:
            missing_keys = [k for k in missing_keys if re.search(pat, k) is None]

    if pt_model._keys_to_ignore_on_load_unexpected is not None:
        for pat in pt_model._keys_to_ignore_on_load_unexpected:
            unexpected_keys = [k for k in unexpected_keys if re.search(pat, k) is None]

    if len(unexpected_keys) > 0:
        logger.warning(
            "Some weights of the TF 2.0 model were not used when initializing the PyTorch model"
            f" {pt_model.__class__.__name__}: {unexpected_keys}\n- This IS expected if you are initializing"
            f" {pt_model.__class__.__name__} from a TF 2.0 model trained on another task or with another architecture"
            " (e.g. initializing a BertForSequenceClassification model from a TFBertForPreTraining model).\n- This IS"
            f" NOT expected if you are initializing {pt_model.__class__.__name__} from a TF 2.0 model that you expect"
            " to be exactly identical (e.g. initializing a BertForSequenceClassification model from a"
            " TFBertForSequenceClassification model)."
        )
    else:
        logger.warning(f"All TF 2.0 model weights were used when initializing {pt_model.__class__.__name__}.\n")
    if len(missing_keys) > 0:
        logger.warning(
            f"Some weights of {pt_model.__class__.__name__} were not initialized from the TF 2.0 model and are newly"
            f" initialized: {missing_keys}\nYou should probably TRAIN this model on a down-stream task to be able to"
            " use it for predictions and inference."
        )
    else:
        logger.warning(
            f"All the weights of {pt_model.__class__.__name__} were initialized from the TF 2.0 model.\n"
            "If your task is similar to the task the model of the checkpoint was trained on, "
            f"you can already use {pt_model.__class__.__name__} for predictions without further training."
        )

    logger.info(f"Weights or buffers not loaded from TF 2.0 model: {all_tf_weights}")

    if output_loading_info:
        loading_info = {"missing_keys": missing_keys, "unexpected_keys": unexpected_keys}
        return pt_model, loading_info

    return pt_model