code: def set_keepalive(self, interval):
          
          self.packetizer.set_keepalive(interval,
              lambda x=weakref.proxy(self): x.global_request('keepalive@lag.net', wait=False))
docs: Turn on/off keepalive packets (default is off).  If this is set, after
          C{interval} seconds without sending any data over the connection, a
          "keepalive" packet will be sent (and ignored by the remote host).  This
          can be useful to keep connections alive over a NAT, for example.
  
          @param interval: seconds to wait before sending a keepalive packet (or
              0 to disable keepalives).
          @type interval: int