Shelve

Have a look at the code below:

import shelve

lib = shelve.open("my_library")
lib["The Chronicles of Narnia"] = ["The Lion, the Witch and the Wardrobe", "Prince Caspian: The Return to Narnia", "The Voyage of the Dawn Treader", "The Silver Chair", "The Horse and His Boy", "The Magician's Nephew", "The Last Battle"]

Looks like something's missing! Write one line that is missing from the code.