Question: who sang at opening ceremony world cup 2018
[{'answer': 'Robbie Williams', 'provenance': [{'wikipedia_id': '57675697', 'title': '2018 FIFA World Cup opening ceremony', 'start_paragraph_id': 9, 'start_character': 19, 'end_paragraph_id': 9, 'end_character': 34, 'bleu_score': 1.0, 'section': 'Section::::Performances.\n'}]}, {'answer': 'Let Me Entertain', 'provenance': [{'wikipedia_id': '57675697', 'title': '2018 FIFA World Cup opening ceremony', 'start_paragraph_id': 9, 'start_character': 101, 'end_paragraph_id': 9, 'end_character': 117, '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': 2411971250422491500}, 'section': 'Section::::Performances.\n'}]}]