Question: who guards former president of the united states
[{'answer': 'Secret Service', 'provenance': [{'wikipedia_id': '16335910', 'title': 'Former Presidents Act', 'start_paragraph_id': 5, 'start_character': 39, 'end_paragraph_id': 5, 'end_character': 53, 'bleu_score': 1.0, 'section': 'Section::::History.\n'}]}, {'provenance': [{'wikipedia_id': '16335910', 'title': 'Former Presidents Act', 'start_paragraph_id': 5, 'start_character': 0, 'end_paragraph_id': 5, 'end_character': 387, 'bleu_score': 0.847012293211405, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 3234739730828987038}, 'section': 'Section::::History.\n'}]}]