Question: how many episodes in it's always sunny season 13
[{'answer': '10', 'provenance': [{'wikipedia_id': '57905879', 'title': "It's Always Sunny in Philadelphia (season 13)", 'start_paragraph_id': 1, 'start_character': 161, 'end_paragraph_id': 1, 'end_character': 163, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]