def test_IMPLEMENTATION(self):
        """
        The server can advertise its implementation string.
        """
        contained(
            self,
            b"IMPLEMENTATION Test Implementation String",
            self.caps, self.pcaps, self.lpcaps
        )

        The server can advertise its implementation string.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/test/test_pop3.py