Question: when was humayun tomb declared a world heritage site
[{'answer': '1993', 'provenance': [{'wikipedia_id': '1355744', 'title': "Humayun's Tomb", 'start_paragraph_id': 2, 'start_character': 560, 'end_paragraph_id': 2, 'end_character': 564, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '1355744', 'title': "Humayun's Tomb", 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 1015, 'bleu_score': 0.852124833269101, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8646590468834677864}, 'section': 'Section::::Abstract.'}]}]