This callback is called form the Crazyflie API when a Crazyflie
        has been connected and the TOCs have been downloaded.

def _connected(self, link_uri):
        """ This callback is called form the Crazyflie API when a Crazyflie
        has been connected and the TOCs have been downloaded."""
        print('Connected to %s' % link_uri)

        self._cf.packet_received.add_callback(self._got_packet)