Question: who has won the 2017 men's single australian open tennis tournament
[{'answer': 'Roger Federer', 'provenance': [{'wikipedia_id': '53014929', 'title': "2017 Australian Open – Men's singles final", 'start_paragraph_id': 1, 'start_character': 165, 'end_paragraph_id': 1, 'end_character': 178, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '53014929', 'title': "2017 Australian Open – Men's singles final", 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 1027, 'bleu_score': 0.8755044071822601, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 16407713305411268169}, 'section': 'Section::::Abstract.'}]}]