anchor.diff:            "You can't push anything to a timeline once it is started");
       Timeline tl = _pool.get();
       tl._parent = _current;
  -    tl._mode = TimelineMode.SEQUENCE;
  +    tl._mode = TimelineMode.sequence;
       _current._children.add(tl);
       _current = tl;
     }
  
positive.code:           "You can't push anything to a timeline once it is started");
      Timeline tl = _pool.get();
      tl._parent = _current;
      tl._mode = TimelineMode.PARALLEL;
      _current._children.add(tl);
      _current = tl;
    }
  
negative.code:       obj.build();
  
        switch (_mode) {
          case TimelineMode.sequence:
            num tDelay = duration;
            duration += obj.fullDuration;
            obj.delay += tDelay;
            break;
  
          case TimelineMode.parallel:
            duration = Math.max(duration, obj.fullDuration);
            break;
        }
  