docs: def bootstrap_counts_singletraj(dtraj, lagtime, n):
      """
      Samples n counts at the given lagtime from the given trajectory
      """
      # check if length is sufficient
      L = len(dtraj)
      if (lagtime > L):
          raise ValueError(
              'Cannot sample counts with lagtime ' + str(lagtime) + ' from a trajectory with length ' + str(L))
      # sample
      I = np.random.randint(0, L - lagtime - 1, size=n)
      J = I + lagtime
  
      # return state pairs
      return (dtraj[I], dtraj[J])