code: def get_stddevs(self, mag, imt, stddev_types, num_sites):
          
          tau = self._get_tau(imt, mag)
          phi = self._get_phi(imt, mag)
          sigma = np.sqrt(tau ** 2. + phi ** 2.)
          stddevs = []
          for stddev_type in stddev_types:
              assert stddev_type in self.DEFINED_FOR_STANDARD_DEVIATION_TYPES
              if stddev_type == const.StdDev.TOTAL:
                  stddevs.append(sigma + np.zeros(num_sites))
              elif stddev_type == const.StdDev.INTRA_EVENT:
                  stddevs.append(phi + np.zeros(num_sites))
              elif stddev_type == const.StdDev.INTER_EVENT:
                  stddevs.append(tau + np.zeros(num_sites))
          return stddevs
docs: Returns the standard deviations for either the ergodic or
          non-ergodic models