Question: when did the byzantine empire stop being roman
[{'answer': '1453', 'provenance': [{'wikipedia_id': '16972981', 'title': 'Byzantine Empire', 'start_paragraph_id': 1, 'start_character': 453, 'end_paragraph_id': 1, 'end_character': 457, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '16972981', 'title': 'Byzantine Empire', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 766, 'bleu_score': 0.7053755161704851, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 9447142082550634870}, 'section': 'Section::::Abstract.'}]}]