Method __replace__

Lib/test/test_copy.py:961–964

(self, **changes)

                self.z = self.x + self.y

            def __replace__(self, **changes):
                x = changes.get('x', self.x)
                y = changes.get('y', self.y)
                return type(self)(x, y)

        attrs = attrgetter('x', 'y', 'z')
        a = A(11, 22)