docs: public static Class<?> getCommonType(Class<?> type1, Class<?> type2) {
  		if (type1 == null) {
  			return type2;
  		}
  		if (type2 == null) {
  			return type1;
  		}
  		Class<?> top = type1;
  		while (!top.isAssignableFrom(type2)) {
  			top = top.getSuperclass();
  			assert top != null;
  		}
  		return top;
  	}