    def gen_function(self) -> str:
        """Generates function source code string.

        Returns
        -------
        str : a string which contains C++ function implementation source code.

        Raises
        ------
        NotImplementedError
        """
        raise NotImplementedError("gen_function is not defined for {}".format(self))
Generates function source code string.

Returns
-------
str : a string which contains C++ function implementation source code.

Raises
------
NotImplementedError
python/aitemplate/compiler/base.py