Question: who was elected mayor of san francisco in 2018
[{'answer': 'former Acting Mayor London Breed', 'provenance': [{'wikipedia_id': '56101986', 'title': '2018 San Francisco mayoral special election', 'start_paragraph_id': 2, 'start_character': 153, 'end_paragraph_id': 2, 'end_character': 185, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '56101986', 'title': '2018 San Francisco mayoral special election', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 415, 'bleu_score': 0.9699161750394991, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 9944779100139682069}, 'section': 'Section::::Abstract.'}]}]