def gen_function_decl(func_attrs) -> str:
    """
    Generate function declaration.

    Returns
    -------
    str
        The function declaration string
    """
    backend_spec = CUDASpec()

    x = func_attrs["inputs"][0]
    input_type = backend_spec.dtype_to_backend_type(x._attrs["dtype"])

    return FUNC_DECL_TEMPLATE.render(
        func_name=func_attrs["name"],
        input_type=input_type,
        index_type=backend_spec.index_type,
    )

    Generate function declaration.

    Returns
    -------
    str
        The function declaration string
    
python/aitemplate/backend/cuda/tensor/index_select.py