Question: an edge of a graph that joins a vertex to itself is called a
[{'answer': 'a loop', 'provenance': [{'wikipedia_id': '1449083', 'title': 'Loop (graph theory)', 'start_paragraph_id': 1, 'start_character': 17, 'end_paragraph_id': 1, 'end_character': 23, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '1449083', 'title': 'Loop (graph theory)', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 141, 'bleu_score': 0.929712191543383, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8342011961737042279}, 'section': 'Section::::Abstract.'}]}]