def state_COMMAND(self, line):
        """
        Handle received lines for the COMMAND state in which commands from the
        client are expected.

        @type line: L{bytes}
        @param line: A received command.
        """
        try:
            return self.processCommand(*line.split(b' '))
        except (ValueError, AttributeError, POP3Error, TypeError) as e:
            log.err()
            self.failResponse('bad protocol or server: {}: {}'.format(
                e.__class__.__name__, e))

        Handle received lines for the COMMAND state in which commands from the
        client are expected.

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