Question: who constructed the massive defensive wall around constantinople in the early 5th century ce
[{'answer': 'Constantine the Great', 'provenance': [{'wikipedia_id': '607447', 'title': 'Walls of Constantinople', 'start_paragraph_id': 1, 'start_character': 216, 'end_paragraph_id': 1, 'end_character': 237, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '607447', 'title': 'Walls of Constantinople', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 845, 'bleu_score': 0.9437230698045791, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 13690501940646943439}, 'section': 'Section::::Abstract.'}]}]