code: static public Bus getBy(String busName){
  		if(busName==null)
  			return get();
  		
  		Bus bus = busMap.get(busName);
  		if(bus==null) {
  			bus=new Bus();
  			busMap.put(busName, bus);
  		}
  		return bus;
  	}
docs: Get bus instance by name
  @param busName bus name
  @return event bus