Question: vincristine acts on which phase of cell cycle
[{'answer': 'metaphase', 'provenance': [{'wikipedia_id': '1102398', 'title': 'Vincristine', 'start_paragraph_id': 14, 'start_character': 197, 'end_paragraph_id': 14, 'end_character': 206, 'bleu_score': 1.0, 'section': 'Section::::Mechanism of action.\n'}]}, {'provenance': [{'wikipedia_id': '1102398', 'title': 'Vincristine', 'start_paragraph_id': 14, 'start_character': 0, 'end_paragraph_id': 14, 'end_character': 241, 'bleu_score': 0.5429658157289601, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 10209560054483749887}, 'section': 'Section::::Mechanism of action.\n'}]}]