private void removeValueFromTree(String valueToRemove){
		Iterator<String> it = _tree.keySet().iterator();
		while(it.hasNext()){
			String parent = it.next();
			
			ArrayList<String> values = _tree.get(parent);
			if(values.contains(valueToRemove)){
				//System.out.println("Removed value " + valueToRemove + " from parent " + parent);
				values.remove(valueToRemove);
			}
			if(values.isEmpty()){
				//System.out.println("Parent " + parent + " is empty and has been removed from tree");
				it.remove();
			}
		}
	}