Question: when does meredith find out pierce is her sister
[{'answer': 'the season ten finale', 'provenance': [{'wikipedia_id': '49447842', 'title': 'Maggie Pierce', 'start_paragraph_id': 1, 'start_character': 366, 'end_paragraph_id': 1, 'end_character': 387, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '49447842', 'title': 'Maggie Pierce', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 609, 'bleu_score': 0.979484453366057, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 11903829344555764392}, 'section': 'Section::::Abstract.'}]}]