Question: when was the dubai metro green line opened to public
[{'answer': 'September 2011 (', 'provenance': [{'wikipedia_id': '17927468', 'title': 'Green Line (Dubai Metro)', 'start_paragraph_id': 3, 'start_character': 323, 'end_paragraph_id': 3, 'end_character': 337, 'bleu_score': 1.0, 'section': 'Section::::Statistics.\n'}]}]