Question: who are they fighting in avengers infinity war
[{'answer': 'Thanos', 'provenance': [{'wikipedia_id': '44240443', 'title': 'Avengers: Infinity War', 'start_paragraph_id': 1, 'start_character': 827, 'end_paragraph_id': 1, 'end_character': 833, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '44240443', 'title': 'Avengers: Infinity War', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 911, 'bleu_score': 0.8715301896223651, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 17062686444164913011}, 'section': 'Section::::Abstract.'}]}]