step 3 item 5 showBooksInUi() should have one parameter

[OrenBochman]

showBooksInUi(books, mBooksTextView);
should be

showBooksInUi(books);
as mBooksTextView is a class var and it is initialised before subscribeUiBooks() is called onCreate()

[mlekena]

Please update the tutorial as this change has been made but the Codelab has not.
https://codelabs.developers.google.com/codelabs/android-persistence/#5