Question: when did cable cars start in san francisco
[{'answer': '1878', 'provenance': [{'wikipedia_id': '1281607', 'title': 'San Francisco cable car system', 'start_paragraph_id': 11, 'start_character': 3, 'end_paragraph_id': 11, 'end_character': 7, 'bleu_score': 1.0, 'section': 'Section::::History.:Expansion.\n'}]}]