docs: def correct(self, z):
          '''Correct the given approximate solution ``z`` with respect to the
          linear system ``linear_system`` and the deflation space defined by
          ``U``.'''
          c = self.linear_system.Ml*(
              self.linear_system.b - self.linear_system.A*z)
          c = utils.inner(self.W, c, ip_B=self.ip_B)
          if self.Q is not None and self.R is not None:
              c = scipy.linalg.solve_triangular(self.R, self.Q.T.conj().dot(c))
          if self.WR is not self.VR:
              c = self.WR.dot(scipy.linalg.solve_triangular(self.VR, c))
          return z + self.W.dot(c)