code: def _get_vector_tile(self, x_tile, y_tile, z_tile):
          
          cache_file = "mapscache/{}.{}.{}.json".format(z_tile, x_tile, y_tile)
          if cache_file not in self._tiles:
              if os.path.isfile(cache_file):
                  with open(cache_file, 'rb') as f:
                      tile = json.loads(f.read().decode('utf-8'))
              else:
                  url = _VECTOR_URL.format(z_tile, x_tile, y_tile, _KEY)
                  data = requests.get(url).content
                  try:
                      tile = mapbox_vector_tile.decode(data)
                      with open(cache_file, mode='w') as f:
                          json.dump(literal_eval(repr(tile)), f)
                  except DecodeError:
                      tile = None
              if tile:
                  self._tiles[cache_file] = [x_tile, y_tile, z_tile, tile, False]
                  if len(self._tiles) > _CACHE_SIZE:
                      self._tiles.popitem(False)
                  self._screen.force_update()
docs: Load up a single vector tile.