code: def trajectory_lengths(self, stride=1, skip=0):
          r
          n = self.ntraj
  
          if not IteratorState.is_uniform_stride(stride):
              return np.fromiter((self.trajectory_length(itraj, stride)
                                  for itraj in range(n)),
                                 dtype=int, count=n)
          else:
              return np.fromiter((self.trajectory_length(itraj, stride, skip)
                                  for itraj in range(n)),
                                 dtype=int, count=n)
docs: r""" Returns the length of each trajectory.
  
          Parameters
          ----------
          stride : int
              return value is the number of frames of the trajectories when
              running through them with a step size of `stride`.
          skip : int
              skip parameter
  
          Returns
          -------
          array(dtype=int) : containing length of each trajectory