code: def peak_generation(self):
          
          if self._peak_generation is None:
              self._peak_generation = sum(
                  [gen.nominal_capacity
                   for gen in self.generators])
  
          return self._peak_generation
docs: Cumulative peak generation capacity of generators of this grid
  
          Returns
          -------
          float
              Ad-hoc calculated or cached peak generation capacity