code: def fit_transform_with(self, estimator, out_ds, fmt=None):
          
          self.fit_with(estimator)
          return self.transform_with(estimator, out_ds, fmt=fmt)
docs: Create a new dataset with the given estimator.
  
          The estimator will be fit by this dataset, and then each trajectory
          will be transformed by the estimator.
  
          Parameters
          ----------
          estimator : BaseEstimator
              This object will be fit and used to transform this dataset
              into a new dataset.
          out_ds : str or Dataset
              This dataset will be transformed and saved into out_ds. If
              out_ds is a path, a new dataset will be created at that path.
          fmt : str
              The type of dataset to create if out_ds is a string.
  
          Returns
          -------
          out_ds : Dataset
              The transformed dataset.
  
          Examples
          --------
          diheds = dataset("diheds")
          tica = diheds.fit_transform_with(tICA(), 'tica')
          kmeans = tica.fit_transform_with(KMeans(), 'kmeans')
          msm = kmeans.fit_with(MarkovStateModel())