Question: how many episodes are in season 1 of this is us
[{'answer': '18', 'provenance': [{'wikipedia_id': '50526957', 'title': 'This Is Us (TV series)', 'start_paragraph_id': 3, 'start_character': 69, 'end_paragraph_id': 3, 'end_character': 71, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]