def get_additional_file_path(model_dir: str, file_name: str) -> Optional[str]:
    """Get the full path to the additional file.

    If file_name is specified, it is assumed to be a file in the model_dir and the full path
    is returned.
    """
    if file_name:
        model_dir = Path(model_dir)
        assert model_dir.is_dir(), f"Model path {model_dir} is not a directory."
        file_path = model_dir / file_name
        assert file_path.exists(), f"{file_name} does not exist in model path directory {model_dir}."
        return str(file_path)
    return None
Get the full path to the additional file.

    If file_name is specified, it is assumed to be a file in the model_dir and the full path
    is returned.
    
olive/model/utils/onnx_utils.py