code: def MAU(self):
          '''Result of preconditioned operator to deflation space, i.e.,
          :math:`MM_lAM_rU`.'''
          if self._MAU is None:
              self._MAU = self.linear_system.M * self.AU
          return self._MAf MAU(self):
          '''Result of preconditioned operator to deflation space, i.e.,
          :math:`MM_lAM_rU`.'''
          if self._MAU is None:
              self._MAU = self.linear_system.M * self.AU
          return self._MAU
docs: Result of preconditioned operator to deflation space, i.e.,
          :math:`MM_lAM_rU`.