Question: when does spirit riding free season 4 start
[{'answer': 'March 16 , 2018', 'provenance': [{'wikipedia_id': '53821955', 'title': 'Spirit Riding Free', 'start_paragraph_id': 23, 'start_character': 285, 'end_paragraph_id': 23, 'end_character': 300, 'bleu_score': 1.0, 'section': 'Section::::Production.\n'}]}]