code: def _check_for_initial_packet_cb(self, data):
          
          self.state = State.CONNECTED
          self.link_established.call(self.link_uri)
          self.packet_received.remove_callback(self._check_for_initial_packet_cb)
docs: Called when first packet arrives from Crazyflie.
  
          This is used to determine if we are connected to something that is
          answering.