Question: who sang at world cup 2018 opening ceremony
[{'answer': 'English pop singer Robbie Williams', 'provenance': [{'wikipedia_id': '57675697', 'title': '2018 FIFA World Cup opening ceremony', 'start_paragraph_id': 9, 'start_character': 0, 'end_paragraph_id': 9, 'end_character': 34, 'bleu_score': 0.668740304976422, 'section': 'Section::::Performances.\n'}]}, {'answer': 'Russian soprano Aida Garifullina', 'provenance': [{'wikipedia_id': '57675697', 'title': '2018 FIFA World Cup opening ceremony', 'start_paragraph_id': 9, 'start_character': 130, 'end_paragraph_id': 9, 'end_character': 162, 'bleu_score': 1.0, 'section': 'Section::::Performances.\n'}]}, {'provenance': [{'wikipedia_id': '57675697', 'title': '2018 FIFA World Cup opening ceremony', 'start_paragraph_id': 9, 'start_character': 0, 'end_paragraph_id': 9, 'end_character': 524, 'bleu_score': 0.5945258210056581, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 13499305482757113774}, 'section': 'Section::::Performances.\n'}]}]