Question: who has the highest hattrick in champions league
[{'answer': 'Lionel Messi', 'provenance': [{'wikipedia_id': '41532657', 'title': 'List of UEFA Champions League hat-tricks', 'start_paragraph_id': 2, 'start_character': 73, 'end_paragraph_id': 2, 'end_character': 85, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]