    def gen_function(self) -> str:
        """call backend functions"""
        current_target = target.Target.current()
        func_key = "{target}.{op}.gen_function".format(
            target=current_target.name(), op=self._attrs["op"]
        )
        func = registry.get(func_key)
        return func(self._attrs)
call backend functions
python/aitemplate/compiler/ops/b2b_bmm/fmha_style_b2b_bmm.py