def lineReceived(self, line):
        """
        Pass a received line to a state machine function.

        @type line: L{bytes}
        @param line: A received line.
        """
        self.resetTimeout()
        getattr(self, 'state_' + self.state)(line)

        Pass a received line to a state machine function.

        @type line: L{bytes}
        @param line: A received line.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/pop3.py