code: def moments(self):
          
          timepoints = self.ma.delays
          response = self.response
          moment1 = statstools.calc_mean_time(timepoints, response)
          moment2 = statstools.calc_mean_time_deviation(
              timepoints, response, moment1)
          return numpy.array([moment1, moment2])
docs: The first two time delay weighted statistical moments of the
          ARMA response.