code: def _guess_format(path):
      
      if os.path.isdir(path):
          return 'dir-npy'
  
      if path.endswith('.h5') or path.endswith('.hdf5'):
          # TODO: Check for mdtraj .h5 file
          return 'hdf5'
  
      # TODO: What about a list of trajectories, e.g. from command line nargs='+'
      return 'mdtraj'
docs: Guess the format of a dataset based on its filename / filenames.