code: def peak_generation(self):
          
          cum_peak_generation = 0
  
          for lv_grid_district in self._lv_grid_districts:
              cum_peak_generation += lv_grid_district.lv_grid.station().peak_generation
  
          return cum_peak_generation
docs: Cumulative peak generation of generators connected to LV grids of 
          underlying LVGDs