Question: when did justin bieber started his music career
[{'answer': '2008', 'provenance': [{'wikipedia_id': '23680998', 'title': 'Justin Bieber', 'start_paragraph_id': 1, 'start_character': 236, 'end_paragraph_id': 1, 'end_character': 240, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '23680998', 'title': 'Justin Bieber', 'start_paragraph_id': 1, 'start_character': 19, 'end_paragraph_id': 1, 'end_character': 655, 'bleu_score': 0.649693579009886, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 9777035080260412200}, 'section': 'Section::::Abstract.'}]}]