A situation that 'Animation._instances' keeps getting fat.

main.py

# This script shows you a situation that 'Animation._instances' keeps getting
# fat. I'm not sure this should be fixed or not.

import gc
from kivy.animation import Animation
from kivy.app import runTouchApp
from kivy.uix.widget import Widget
from kivy.clock import Clock


# If you run this script on master branch, you have to implement
# 'Parallel.cancel_property()'. For example like this:
# from kivy.animation import Parallel, Sequence
# Parallel.cancel_property = Sequence.cancel_property


def func(*args):
    gc.collect()
    print(Animation._instances)
    anim = Animation(x=100) & Animation(y=100)
    target = Widget()
    anim.start(target)
    Clock.schedule_once(lambda *args: anim.cancel_property(target, 'x'), .5)


Clock.schedule_interval(func, 1.2)
runTouchApp(Widget())