Question: who was the most powerful witch in charmed
[{'answer': 'Prue', 'provenance': [{'wikipedia_id': '345231', 'title': 'Prue Halliwell', 'start_paragraph_id': 0, 'start_character': 0, 'end_paragraph_id': 0, 'end_character': 4, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '345231', 'title': 'Prue Halliwell', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 1203, 'bleu_score': 0.990171692033262, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 1251460118393921279}, 'section': 'Section::::Abstract.'}]}]