def _update_expiry(self, session_id, session_data):
    return self._store_session(session_id, session_data)
Gets distance in metres to the current waypoint. 
dataset/ETHPy150Open JeremyOT/Toto/toto/dbconnection.py/DBConnection._update_expiry--crossover with--dataset/ETHPy150Open dronekit/dronekit-python/examples/mission_basic/mission_basic.py/distance_to_current_waypoint