input: Write a python function to create a dictionary with book titles as keys and authors as values from a list of Book objects.
  assert create_book_dict([Book("Great Expectations", "Charles Dickens", "123-456-789"), Book("Brave New World", "Aldous Huxley", "987-654-321")]) == {"Great Expectations": "Charles Dickens", "Brave New World": "Aldous Huxley"}
  assert create_book_dict([Book("1984", "George Orwell", "111-222-333"), Book("To Kill a Mockingbird", "Harper Lee", "444-555-666")]) == {"1984": "George Orwell", "To Kill a Mockingbird": "Harper Lee"}
output: def create_book_dict(books):
      return {book.title: book.author for book in books}