(str, list(str), list(str)): Function signature as
            (name, list parameters type, list return values type)

def signature(self):
        """
            (str, list(str), list(str)): Function signature as
            (name, list parameters type, list return values type)
        """
        return self.name, [str(x.type) for x in self.parameters], [str(x.type) for x in self.returns]