public void flip() {
        mFlipToSide = !mFlipToSide;
        if (mFlipAnimator.isStarted()) {
            mFlipAnimator.reverse();
        } else {
            if (!mFlipToSide /* front to back */) {
                mFlipAnimator.start();
            } else /* back to front */ {
                mFlipAnimator.reverse();
            }
        }
    }
Starts an animated flip to the other side. If a flip animation is currently started,
it will be reversed.
android/modules/module_common/src/main/java/github/tornaco/android/thanos/widget/checkable/FlipDrawable.java