code: def weather_cells(self):
          
          if not self._weather_cells:
  
              # get all the weather cell ids
              self._weather_cells = []
              for gen in self.generators:
                  if hasattr(gen, 'weather_cell_id'):
                      self._weather_cells.append(gen.weather_cell_id)
  
              # drop duplicates
              self._weather_cells = list(set(self._weather_cells))
              # no need to check for Nones in the list because None in
              # gen.weather_cell_id is kicked out by the if hasattr() before
  
          return self._weather_cells
docs: Weather cells contained in grid
  
          Returns
          -------
          list
              list of weather cell ids contained in grid