code: def derivative(self, point):
          
          if self.pad_mode == 'constant' and self.pad_const != 0:
              return ResizingOperator(
                  domain=self.domain, range=self.range, pad_mode='constant',
                  pad_const=0.0)
          else:  # operator is linear
              return self
docs: Derivative of this operator at ``point``.
  
          For the particular case of constant padding with non-zero
          constant, the derivative is the corresponding zero-padding
          variant. In all other cases, this operator is linear, i.e.
          the derivative is equal to ``self``.