Question: which u.s. president had a cocker spaniel named checkers
[{'answer': 'Richard Nixon', 'provenance': [{'wikipedia_id': '400508', 'title': 'United States presidential pets', 'start_paragraph_id': 6, 'start_character': 0, 'end_paragraph_id': 6, 'end_character': 13, 'bleu_score': 1.0, 'section': 'Section::::History of White House dogs.\n'}]}, {'provenance': [{'wikipedia_id': '400508', 'title': 'United States presidential pets', 'start_paragraph_id': 6, 'start_character': 0, 'end_paragraph_id': 6, 'end_character': 618, 'bleu_score': 0.9817332376369081, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 2366699323669152521}, 'section': 'Section::::History of White House dogs.\n'}]}]