code: def update_pop(self):
          
          candidates = []
          for ind in self.population:
              candidates.append(self.crossover(ind))
          self._params['model_count'] += len(candidates)
          self.assign_fitnesses(candidates)
          for i in range(len(self.population)):
              if candidates[i].fitness > self.population[i].fitness:
                  self.population[i] = candidates[i]
docs: Updates the population according to crossover and fitness criteria.