code: public boolean removeObserver(BusObserver<M> observer) {
  		logger.trace("removing observer {}", observer.getClass().getSimpleName());
  		return observers.remove(observer);
  	}
docs: Removes the given object from the set of registered observers.
  
  @param observer
  the observer to be removed.
  @return
  <code>true</code> if the object was in the set of registered observers,
  <code>false</code> otherwise.