Question: where is the substantia nigra located in the brain
[{'answer': 'midbrain', 'provenance': [{'wikipedia_id': '46425', 'title': 'Substantia nigra', 'start_paragraph_id': 1, 'start_character': 70, 'end_paragraph_id': 1, 'end_character': 78, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '46425', 'title': 'Substantia nigra', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 561, 'bleu_score': 0.931506586060527, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 3442145342541370465}, 'section': 'Section::::Abstract.'}]}]