code: function(task) {
  
  		if (this._active_tasks.indexOf(task) == -1) {
  
  			this._active_tasks.push(task);
  
  		}
  
  		this._enable();
  
  		if (!this.is_running) {
  			this._enable();
  			this.is_running = true;
  		}
  
  	}
docs: Start animating
  @param {Lava.animation.Abstract} task