code: def keep_alive(self, period=1, margin=.3):
          
          asyncio.ensure_future(self.core.keep_alive(period, margin))
docs: Periodically send a keep alive message to the Arduino.
          Frequency of keep alive transmission is calculated as follows:
          keep_alive_sent = period - (period * margin)
  
  
          :param period: Time period between keepalives.
                         Range is 0-10 seconds. 0 disables
                         the keepalive mechanism.
  
          :param margin: Safety margin to assure keepalives
                          are sent before period expires. Range is 0.1 to 0.9
  
          :returns: No return value