code: def get_feature_names(self):
          
          feature_names = []
          for name, trans, weight in self._iter():
              if not hasattr(trans, 'get_feature_names'):
                  raise AttributeError("Transformer %s (type %s) does not "
                                       "provide get_feature_names."
                                       % (str(name), type(trans).__name__))
              feature_names.extend([name + "__" + f for f in
                                    trans.get_feature_names()])
          return feature_names
docs: Get feature names from all transformers.
  
          Returns
          -------
          feature_names : list of strings
              Names of the features produced by transform.