code: public void setEngine(final ActionEngine engine) {
  	if (!Objects.equals(this.engine, engine)) { // Only if changed
  	    synchronized (contexts) {
  		contexts.clear();
  	    }
  	}
  	this.engine = engine;
      }
docs: Associates a engine to this scheduler (if the engine changes all task references are lost).
  
  @param engine
  Engine to schedule actions against.