@classmethod
def deriv(cls, num1, deriv1, num2, deriv2):
    """Differentiate the expression at the given values

        :param num1: Number -- Value of parent 1
        :param deriv1: Number -- Value of derivative of parent 1
        :param num2: Number -- Value of parent 2
        :param deriv2: Number -- Value of parent 2
        :return:
        """
    raise NotImplementedError()
