Call ``method_name`` with args and kwargs on each member.

        Returns a sequence of return values.

def _apply(self, method_name, *args, **kwargs):
        """Call ``method_name`` with args and kwargs on each member.

        Returns a sequence of return values.

        """

        return [
            getattr(member, method_name)(*args, **kwargs)
            for member in self.forms
        ]