code: def derivative(self, x):
          
          return self.scalar * self.operator.derivative(self.scalar * x)
docs: Return the derivative at ``x``.
  
          The derivative of the right scalar operator multiplication
          follows the chain rule:
  
              ``OperatorRightScalarMult(op, s).derivative(y) ==
              OperatorLeftScalarMult(op.derivative(s * y), s)``
  
          Parameters
          ----------
          x : `domain` `element-like`
              Evaluation point of the derivative.
  
          Examples
          --------
          >>> space = odl.rn(3)
          >>> operator = odl.IdentityOperator(space) - space.element([1, 1, 1])
          >>> left_mul_op = OperatorRightScalarMult(operator, 3)
          >>> derivative = left_mul_op.derivative([0, 0, 0])
          >>> derivative([1, 1, 1])
          rn(3).element([ 3.,  3.,  3.])