def set_keepalive(self, interval, callback):
self.__keepalive_interval = interval<EOL>self.__keepalive_callback = callback<EOL>self.__keepalive_last = time.time()<EOL>
Turn on/off the callback keepalive.  If C{interval} seconds pass with
no data read from or written to the socket, the callback will be
executed and the timer will be reset.