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