Question: when did messi started playing soccer for barcelona
[{'answer': '2003', 'provenance': [{'wikipedia_id': '2150841', 'title': 'Lionel Messi', 'start_paragraph_id': 12, 'start_character': 11, 'end_paragraph_id': 12, 'end_character': 15, 'bleu_score': 1.0, 'section': 'Section::::Club career.:Barcelona.\n'}]}]