To simplify your development process, we've provided a backend server for you to develop against. The provided file BooksAPI.js contains the methods you will need to perform necessary operations on the backend:
Method Signature:
``js
getAll()
`
* Returns a Promise which resolves to a JSON object containing a collection of book objects.
* This collection represents the books currently in the bookshelves in your app.
### update
Method Signature:
`js
update(book, shelf)
`
* book: