code: private boolean passesFilters(Level3Element ele)
  	{
  		if (filters == null) return true;
  
  		for (Filter filter : filters)
  		{
  			if (!filter.okToTraverse(ele)) return false;
  		}
  		return true;
  	}
docs: There must be no filter opposing to traverse this object to traverse it.
  @param ele element to check
  @return true if ok to traverse