code: def best_periods(self):
          
          for (key, model) in self.models_.items():
              model.optimizer = self.optimizer
  
          return dict((filt, model.best_period)
                      for (filt, model) in self.models_.items())
docs: Compute the scores under the various models
  
          Parameters
          ----------
          periods : array_like
              array of periods at which to compute scores
  
          Returns
          -------
          best_periods : dict
              Dictionary of best periods. Dictionary keys are the unique filter
              names passed to fit()