code: def adjoint(self):
          
          if not self.is_linear:
              raise ValueError('operator with nonzero pad_const ({}) is not'
                               ' linear and has no adjoint'
                               ''.format(self.pad_const))
  
          return -PartialDerivative(self.range, self.axis, self.domain,
                                    _ADJ_METHOD[self.method],
                                    _ADJ_PADDING[self.pad_mode],
                                    self.pad_const)
docs: Return the adjoint operator.