Request for More Specific Instructions for `stack_compress`

The instructions is a little unclear for me

from cpprb import ReplayBuffer

rb = ReplayBuffer(32,{"obs":{"shape": (16,16)}, 'rew': {}, 'done': {}},
                  next_of = "obs", stack_compress = "obs")

rb.add(obs=(np.ones((16,16))),
       next_obs=(np.ones((16,16))),
       rew=1,
       done=0)

So usually a stacked frame would look something like

obs = np.ones((16,16,4)) # stack of 4 16x16 frames

Is np.ones((16,16)) supposed to be one of the stacked frames? Do you have a more complete example to show how it works by any chance? Thanks.