docs: def determine_lengths(dtrajs):
      r"""
      Determines the lengths of all trajectories
  
      Parameters
      ----------
      dtrajs : list of int-arrays
          discrete trajectories
      """
      if (isinstance(dtrajs[0], (int))):
          return len(dtrajs) * np.ones((1))
      lengths = np.zeros((len(dtrajs)))
      for i in range(len(dtrajs)):
          lengths[i] = len(dtrajs[i])
      return lengths