Question: who wrote the song baby by justin bieber
[{'answer': 'Bieber', 'provenance': [{'wikipedia_id': '25788953', 'title': 'Baby (Justin Bieber song)', 'start_paragraph_id': 0, 'start_character': 13, 'end_paragraph_id': 0, 'end_character': 19, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': "Christopher `` Tricky '' Stewart"}, {'answer': "Terius `` The - Dream '' Nash"}, {'provenance': [{'wikipedia_id': '25788953', 'title': 'Baby (Justin Bieber song)', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 370, 'bleu_score': 0.968982777549629, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 11823085383960589011}, 'section': 'Section::::Abstract.'}]}]