code: public synchronized EventBus bindSync(SysEventId sysEventId, SysEventListener sysEventListener) {
          return _bind(sysEventListeners, sysEventId, sysEventListener);
      }
docs: Bind an {@link SysEventListener} to a {@link SysEventId} synchronously.
  
  **Note** this method is not supposed to be called by user application
  directly.
  
  @param sysEventId
  the {@link SysEventId system event ID}
  @param sysEventListener
  an instance of {@link SysEventListener}
  @return this event bus instance
  @see #bind(SysEventId, SysEventListener)