question: public static GroupCategorySet union ( GroupCategorySet one , GroupCategorySet two ) { Assert . isNotNull ( one ) ; Assert . isNotNull ( two ) ; if ( one == two ) return one ; if ( one == NONE ) return two ; if ( two == NONE ) return one ; Set combined = new HashSet ( ) ; combined . addAll ( one . asList ( ) ) ; combined . addAll ( two . asList ( ) ) ; return new GroupCategorySet ( combined ) ; }
target:  Creates a new group category set containing the union of the given two group category sets