69     def diff_diff(self, other):  argument
71         old = other.x if other else 0
80     def ratio(self, other):  argument
82         old = other.x if other else 0
96     def __add__(self, other):  argument
97         return self.__class__(self.x + other.x)
99     def __sub__(self, other):  argument
100         return self.__class__(self.x - other.x)
102     def __mul__(self, other):  argument
103         return self.__class__(self.x * other.x)
117     def __add__(self, other):  argument
119             self.size + other.size)