Question: when was royal caribbean liberty of the seas built
[{'answer': 'May 2007', 'provenance': [{'wikipedia_id': '4731451', 'title': 'Liberty of the Seas', 'start_paragraph_id': 1, 'start_character': 88, 'end_paragraph_id': 1, 'end_character': 96, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '4731451', 'title': 'Liberty of the Seas', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 568, 'bleu_score': 0.674367308085704, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 16813573203435959384}, 'section': 'Section::::Abstract.'}]}]