def is_stub_def(self) -> bool:
        """Is this line a function definition with a body consisting only of "..."?"""
        return self.is_def and self.leaves[-4:] == [Leaf(token.COLON, ":")] + [
            Leaf(token.DOT, ".") for _ in range(3)
        ]
Is this line a function definition with a body consisting only of "..."?
src/black/lines.py