Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.

[EX Q]: Which Chuck Berry song is performed by Marty McFly at the end of the film Back to the Future?
[EX A]: back to the future

[EX Q]: What is the name of the astromech droid companion of Anakin Skywalker, Luke Skywalker and Obi-Wan Kenobi in the Star Wars franchise?
[EX A]: droid

[EX Q]: Which former Portuguese African Colony joined the British Commonwealth in 1995?
[EX A]:
commonwealth of nations