Load data from an external file for tensor.

    @params
    tensor: a TensorProto object.
    base_dir: directory that contains the external data.

def load_external_data_for_tensor(tensor, base_dir):  # type: (TensorProto, Text) -> None
    """
    Load data from an external file for tensor.

    @params
    tensor: a TensorProto object.
    base_dir: directory that contains the external data.
    """
    if tensor.HasField("raw_data"):  # already loaded
        return
    info = ExternalDataInfo(tensor)
    file_location = _sanitize_path(info.location)
    external_data_file_path = os.path.join(base_dir, file_location)

    with open(external_data_file_path, 'rb') as data_file:

        if info.offset:
            data_file.seek(info.offset)

        if info.length:
            tensor.raw_data = data_file.read(info.length)
        else:
            tensor.raw_data = data_file.read()