def listen(self):
self.listening = True<EOL>if self.threading:<EOL><INDENT>from threading import Thread<EOL>self.listen_thread = Thread(target=self.listen_loop)<EOL>self.listen_thread.daemon = True<EOL>self.listen_thread.start()<EOL>self.scheduler_thread = Thread(target=self.scheduler)<EOL>self.scheduler_thread.daemon = True<EOL>self.scheduler_thread.start()<EOL><DEDENT>else:<EOL><INDENT>self.listen_loop()<EOL><DEDENT>
Starts the listen loop. If threading is enabled, then the loop will
        be started in its own thread.

        Args:
          None

        Returns:
          None