Question: what is best thing i never had song about
[{'answer': 'revenge and karma', 'provenance': [{'wikipedia_id': '31923733', 'title': 'Best Thing I Never Had', 'start_paragraph_id': 2, 'start_character': 67, 'end_paragraph_id': 2, 'end_character': 84, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'revenge', 'provenance': [{'wikipedia_id': '31923733', 'title': 'Best Thing I Never Had', 'start_paragraph_id': 2, 'start_character': 67, 'end_paragraph_id': 2, 'end_character': 74, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'karma', 'provenance': [{'wikipedia_id': '31923733', 'title': 'Best Thing I Never Had', 'start_paragraph_id': 2, 'start_character': 79, 'end_paragraph_id': 2, 'end_character': 84, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '31923733', 'title': 'Best Thing I Never Had', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 563, 'bleu_score': 0.979896933041101, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15963108959411169963}, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '31923733', 'title': 'Best Thing I Never Had', 'section': 'Section::::Composition and lyrical interpretation.\n', 'start_paragraph_id': 14, 'end_paragraph_id': 14, 'meta': {'evidence_span': ['relationship between Beyoncé and her lover, a situation that suits both of them. They also touch on revenge and karma,', 'They also touch on revenge and karma, particularly the opening line', 'They also touch on revenge and karma, particularly the opening line, "What goes around comes back around", the lines "Best thing I never had", "Best thing you never had", and the closing line, "Sucks to be you right now".']}}]}, {'provenance': [{'wikipedia_id': '31923733', 'title': 'Best Thing I Never Had', 'section': 'Section::::Abstract.', 'start_paragraph_id': 2, 'end_paragraph_id': 2, 'meta': {'evidence_span': ['A pop and R&B ballad, the subjects of "Best Thing I Never Had" are revenge and karma.', 'A pop and R&B ballad, the subjects of "Best Thing I Never Had" are revenge and karma', 'A pop and R&B ballad, the subjects of "Best Thing I Never Had" are revenge and karma.']}}]}]