def _get_closest_island_distance(self, action):
next_move_segment = Segment(self._world_map.robot.get_center(),
action.destination)
closest_island = self._get_closest_island_from_segment(
next_move_segment)
if closest_island is None:
return None
return next_move_segment.distance(
closest_island.get_center()) - closest_island.get_size() / 2
