Question: who is the song jar of hearts about
[{'answer': 'an ex-boyfriend', 'provenance': [{'wikipedia_id': '27975110', 'title': 'Jar of Hearts', 'start_paragraph_id': 8, 'start_character': 84, 'end_paragraph_id': 8, 'end_character': 99, 'bleu_score': 1.0, 'section': 'Section::::Theme and composition.\n'}]}, {'provenance': [{'wikipedia_id': '27975110', 'title': 'Jar of Hearts', 'start_paragraph_id': 8, 'start_character': 0, 'end_paragraph_id': 8, 'end_character': 530, 'bleu_score': 0.947703439108541, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6736697996238999063}, 'section': 'Section::::Theme and composition.\n'}]}]