docs: def ctime(message=None):
      "Counts the time spent in some context"
      global t_elapsed
      t_elapsed = 0.0
      print('\n')
      t = time.time()
      yield
      if message:
          print(message + ":  ", end='')
      t_elapsed = time.time() - t
      print(round(t_elapsed, 4), "sec")