code: def save_dtrajs(self, prefix='', output_dir='.',
                      output_format='ascii', extension='.dtraj'):
          r
  
          clustering = self._chain[-1]
          reader = self._chain[0]
          from pyemma.coordinates.clustering.interface import AbstractClustering
          assert isinstance(clustering, AbstractClustering)
  
          trajfiles = None
          if isinstance(reader, FeatureReader):
              trajfiles = reader.filenames
  
          clustering.save_dtrajs(
              trajfiles, prefix, output_dir, output_format, extension)
docs: r"""Saves calculated discrete trajectories. Filenames are taken from
          given reader. If data comes from memory dtrajs are written to a default
          filename.
  
  
          Parameters
          ----------
          prefix : str
              prepend prefix to filenames.
          output_dir : str (optional)
              save files to this directory. Defaults to current working directory.
          output_format : str
              if format is 'ascii' dtrajs will be written as csv files, otherwise
              they will be written as NumPy .npy files.
          extension : str
              file extension to append (eg. '.itraj')