Question: when did the ravens last won a superbowl
[{'answer': '2012', 'provenance': [{'wikipedia_id': '4293', 'title': 'Baltimore Ravens', 'start_paragraph_id': 3, 'start_character': 180, 'end_paragraph_id': 3, 'end_character': 184, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]