code: def population(self):
          "Class containing the population and all the individuals generated"
          try:
              return self._p
          except AttributeError:
              self._p = self._population_class(base=self,
                                               tournament_size=self._tournament_size,
                                               classifier=self.classifier,
                                               labels=self._labels,
                                               es_extra_test=self.es_extra_test,
                                               popsize=self._popsize,
                                               random_generations=self._random_generations,
                                               negative_selection=self._negative_selection)
              return self._f population(self):
          "Class containing the population and all the individuals generated"
          try:
              return self._p
          except AttributeError:
              self._p = self._population_class(base=self,
                                               tournament_size=self._tournament_size,
                                               classifier=self.classifier,
                                               labels=self._labels,
                                               es_extra_test=self.es_extra_test,
                                               popsize=self._popsize,
                                               random_generations=self._random_generations,
                                               negative_selection=self._negative_selection)
              return self._p
docs: Class containing the population and all the individuals generated