def test21_filter_success(self):
book_collection = BookCollection(**self.valid_bookcoll_kwargs)
book_collection[self.test_book1.isbn] = self.test_book1
book_collection[self.test_book2.isbn] = self.test_book2
self.assertEqual(
book_collection.filter(key='isbn')[0], self.test_book1)
self.assertEqual(
book_collection.filter(key='genre')[0], self.test_book2)
def test22_filter_attr_not_found_fail(self):
book_collection = BookCollection(**self.valid_bookcoll_kwargs)
book_collection[self.test_book1.isbn] = self.test_book1
with self.assertRaises(KeyError):
book_collection.filter(key='invalid')