Question: what is the shape of mandatory traffic signs
[{'answer': 'circular', 'provenance': [{'wikipedia_id': '13263364', 'title': 'Mandatory sign', 'start_paragraph_id': 1, 'start_character': 246, 'end_paragraph_id': 1, 'end_character': 254, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '13263364', 'title': 'Mandatory sign', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 436, 'bleu_score': 0.9735040436119741, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 9231822871672930248}, 'section': 'Section::::Abstract.'}]}]