'Start sending I{PING} messages every L{IRCClient.heartbeatInterval}
seconds to keep the connection to the server alive during periods of no
activity.
@since: 11.1'

def startHeartbeat(self):

    self.stopHeartbeat()
    if (self.heartbeatInterval is None):
        return
    self._heartbeat = self._createHeartbeat()
    self._heartbeat.start(self.heartbeatInterval, now=False)
