code: def _regressors(self):
          
  
          # sklearn version < 0.18.0
          regressors = ()
  
          # sklearn version >= 0.18.0
          if self.sklearn_ver[:2] >= (0, 18):
              from sklearn.neural_network.multilayer_perceptron \
                  import MLPRegressor
              regressors += (MLPRegressor, )
  
          return regressors
docs: Get a set of supported regressors.
  
          Returns
          -------
          regressors : {set}
              The set of supported regressors.