code: public synchronized static <D extends Dao<T, ?>, T> D lookupDao(ConnectionSource connectionSource, Class<T> clazz) {
  		if (connectionSource == null) {
  			throw new IllegalArgumentException("connectionSource argument cannot be null");
  		}
  		ClassConnectionSource key = new ClassConnectionSource(connectionSource, clazz);
  		Dao<?, ?> dao = lookupDao(key);
  		@SuppressWarnings("unchecked")
  		D castDao = (D) dao;
  		return castDao;
  	}
docs: Helper method to lookup a DAO if it has already been associated with the class. Otherwise this returns null.