Question: when was the first stone pyramid built in egypt
[{'answer': '2630 BC -- 2611 BC'}, {'provenance': [{'wikipedia_id': '864667', 'title': 'Egyptian pyramids', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 375, 'bleu_score': 0.8394625298693851, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 16047921739154953521}, 'section': 'Section::::Abstract.'}]}]