Question: who defeated obi-wan kenobi in a lightsaber duel
[{'answer': 'Vader', 'provenance': [{'wikipedia_id': '56196', 'title': 'Obi-Wan Kenobi', 'start_paragraph_id': 1, 'start_character': 542, 'end_paragraph_id': 1, 'end_character': 547, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '56196', 'title': 'Obi-Wan Kenobi', 'start_paragraph_id': 6, 'start_character': 0, 'end_paragraph_id': 6, 'end_character': 1167, 'bleu_score': 0.9544921379483321, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 1373754526332099506}, 'section': 'Section::::Appearances.:Original trilogy.\n'}]}]