code: def fit_transform(self, X, y=None, **params):
          '''
          Fit and transform the stacked points.
  
          Parameters
          ----------
          X : :class:`Features` or list of bag feature arrays
              Data to train on and transform.
  
          any other keyword argument :
              Passed on as keyword arguments to the transformer's ``transform()``.
  
          Returns
          -------
          X_new : :class:`Features`
              Transformed features.
          '''
          X = as_features(X, stack=True)
          X_new = self.transformer.fit_transform(X.stacked_features, y, **params)
          return self._gather_outputs(X, X_newf fit_transform(self, X, y=None, **params):
          '''
          Fit and transform the stacked points.
  
          Parameters
          ----------
          X : :class:`Features` or list of bag feature arrays
              Data to train on and transform.
  
          any other keyword argument :
              Passed on as keyword arguments to the transformer's ``transform()``.
  
          Returns
          -------
          X_new : :class:`Features`
              Transformed features.
          '''
          X = as_features(X, stack=True)
          X_new = self.transformer.fit_transform(X.stacked_features, y, **params)
          return self._gather_outputs(X, X_new)
docs: Fit and transform the stacked points.
  
          Parameters
          ----------
          X : :class:`Features` or list of bag feature arrays
              Data to train on and transform.
  
          any other keyword argument :
              Passed on as keyword arguments to the transformer's ``transform()``.
  
          Returns
          -------
          X_new : :class:`Features`
              Transformed features.