code: def xstep(self):
          r
  
          self.X = sl.idctii(self.Gamma*sl.dctii(self.Y + self.S - self.U,
                                                 axes=self.axes), axes=self.axes)
          if self.opt['LinSolveCheck']:
              self.xrrs = sl.rrs(
                  self.X + (self.lmbda/self.rho) *
                  sl.idctii((self.Alpha**2) *
                            sl.dctii(self.X, axes=self.axes),
                            axes=self.axes), self.Y + self.S - self.U)
          else:
              self.xrrs = None
docs: r"""Minimise Augmented Lagrangian with respect to
          :math:`\mathbf{x}`.