docs: public LabelAlphabet DefaultLabelAlphabet()	{
  		IAlphabet alphabet = null;
  		if (!maps.containsKey(DefalutLabelName))	{
  			maps.put(DefalutLabelName, new LabelAlphabet());
  			alphabet = maps.get(DefalutLabelName);
  		}else	{
  			alphabet = maps.get(DefalutLabelName);
  			if (!(alphabet instanceof LabelAlphabet))	{
  				throw new ClassCastException();
  			}
  		}
  		return (LabelAlphabet) alphabet;
  	}