$def with (user, book, expiry_days) $var subject: Have you finished reading $book.title? Hello $user.displayname, Some people are waiting to borrow "$book.title", a book you have currently borrowed from Open Library. Your loan is scheduled to last for $expiry_days more days, but if you're finished reading the book, please feel free to return it early so that the next person can borrow it. To return the book, please visit: $book.url("/borrow", relative=False) Thank you for using Open Library. Sincerely, The Open Library Team