Go straight down and turn off the motors.

        Do not call this function if you use the with keyword. Landing is
        done automatically when the context goes out of scope.

        :param velocity: The velocity (meters/second) when going down
        :return:

def land(self, velocity=DEFAULT):
        """
        Go straight down and turn off the motors.

        Do not call this function if you use the with keyword. Landing is
        done automatically when the context goes out of scope.

        :param velocity: The velocity (meters/second) when going down
        :return:
        """
        if self._is_flying:
            duration_s = self._z / self._velocity(velocity)
            self._hl_commander.land(0, duration_s)
            time.sleep(duration_s)
            self._z = 0.0

            self._hl_commander.stop()
            self._is_flying = False