docs: def _filter_closest(self, lat, lon, stations):
          """Helper to filter the closest station to a given location."""
          current_location = (lat, lon)
          closest = None
          closest_distance = None
  
          for station in stations:
              station_loc = (station.latitude, station.longitude)
              station_distance = distance.distance(current_location,
                                                   station_loc).km
              if not closest or station_distance < closest_distance:
                  closest = station
                  closest_distance = station_distance
  
          return closest