Question: how were transformation masks used in the original potlatch ceremonies
[{'answer': 'to illustrate myths', 'provenance': [{'wikipedia_id': '23008897', 'title': 'Transformation mask', 'start_paragraph_id': 1, 'start_character': 323, 'end_paragraph_id': 1, 'end_character': 342, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '23008897', 'title': 'Transformation mask', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 402, 'bleu_score': 0.970795021215021, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 7038951996695039948}, 'section': 'Section::::Abstract.'}]}]