Who is the main protagonist of the Metroid franchise?
{'directed': True, 'multigraph': False, 'graph': {}, 'nodes': [{'type': 'QUESTIONS_ENTITY', 'name_': 'Q12397', 'id': 0, 'label': 'Metroid'}, {'type': 'INTERNAL', 'name_': 'Q20212568', 'id': 1, 'label': 'Metroid universe'}, {'type': 'ANSWER_CANDIDATE_ENTITY', 'name_': 'Q2012171', 'id': 2, 'label': 'Metroid: Zero Mission'}], 'links': [{'name_': 'P1445', 'source': 1, 'target': 0, 'label': 'fictional universe described in'}, {'name_': 'P1445', 'source': 1, 'target': 2, 'label': 'fictional universe described in'}]}