docs: def compute_cusum_ts(self, ts):
          """ Compute the Cumulative Sum at each point 't' of the time series. """
          mean = np.mean(ts)
          cusums = np.zeros(len(ts))
          cusum[0] = (ts[0] - mean)
          for i in np.arange(1, len(ts)):
              cusums[i] = cusums[i - 1] + (ts[i] - mean)
  
          assert(np.isclose(cumsum[-1], 0.0))
          return cusums