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 - Divergence(domain=self.range, range=self.domain,
                              method=_ADJ_METHOD[self.method],
                              pad_mode=_ADJ_PADDING[self.pad_mode],
                              pad_const=self.pad_const)
docs: Adjoint of this operator.
  
          The adjoint is given by the negative `Divergence` with corrections for
          the method and padding.
  
          The Divergence is constructed from a ``space`` as a product space
          operator ``space^n --> space``, hence we need to provide the domain of
          this operator.