method containsTweens

Source

bool containsTweens(TweenObject tweenObject) {

  var link = _firstAnimatableLink;
  while (identical(link, _lastAnimatableLink) == false) {
    var animatable = link.animatable;
    if (animatable is Tween && identical(animatable.tweenObject, tweenObject)) {
      return true;
    }
    link = link.nextAnimatableLink;
  }

  return false;
}