Question: what is the purpose of the sierra club
[{'answer': 'promote environmentalist policies', 'provenance': [{'wikipedia_id': '242098', 'title': 'Sierra Club', 'start_paragraph_id': 2, 'start_character': 202, 'end_paragraph_id': 2, 'end_character': 235, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '242098', 'title': 'Sierra Club', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 541, 'bleu_score': 0.9738505480425671, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 10045235918868889254}, 'section': 'Section::::Abstract.'}]}]