Question: when was the last time the steelers played in the super bowl
[{'answer': 'February 6 , 2011', 'provenance': [{'wikipedia_id': '23338', 'title': 'Pittsburgh Steelers', 'start_paragraph_id': 20, 'start_character': 1515, 'end_paragraph_id': 20, 'end_character': 1532, 'bleu_score': 1.0, 'section': 'Section::::Franchise history.:The Mike Tomlin era.\n'}]}, {'provenance': [{'wikipedia_id': '23338', 'title': 'Pittsburgh Steelers', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 759, 'bleu_score': 0.8190756949548751, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15632361852762452537}, 'section': 'Section::::Abstract.'}]}]