code: def derivative(self, point=None):
          
          if self.pad_mode == 'constant' and self.pad_const != 0:
              return Laplacian(self.domain, self.range,
                               pad_mode=self.pad_mode, pad_const=0)
          else:
              return self
docs: Return the derivative operator.
  
          The Laplacian is usually linear, but in case the 'constant'
          ``pad_mode`` is used with nonzero ``pad_const``, the
          derivative is given by the derivative with 0 ``pad_const``.
  
          Parameters
          ----------
          point : ``domain`` element, optional
              The point to take the derivative in. Does not change the result
              since the operator is affine.