def METHOD_NAME(
    self,
) -> tuple[float, float, float]:
    '''
    Compute the "downsampling" ratio info between the historical shm
    buffer and the real-time (HFT) one.
    Return a tuple of the fast sample period, historical sample
    period and ratio between them.
    '''
    times = self.hist_shm.array['time']
    end = pendulum.from_timestamp(times[-1])
    start = pendulum.from_timestamp(times[times != times[-1]][-1])
    hist_step_size_s = (end - start).seconds
    times = self.rt_shm.array['time']
    end = pendulum.from_timestamp(times[-1])
    start = pendulum.from_timestamp(times[times != times[-1]][-1])
    rt_step_size_s = (end - start).seconds
    ratio = hist_step_size_s / rt_step_size_s
    return (
        rt_step_size_s,
        hist_step_size_s,
        ratio,
    )