public List<Map<String, ?>> getBooksWithMember(Long memberId) {
   Preconditions.checkNotNull(memberId);
   booksWithMember = libraryFinder.findAllBooksWithMember(memberId);
   return booksWithMember;
 }
 public List<Map<String, ?>> getAllBooks() {
   allBooks = libraryFinder.findAllBooks();
   return allBooks;
 }