Question: what is the pigmented layer of the eyes iris
[{'answer': 'stroma', 'provenance': [{'wikipedia_id': '86801', 'title': 'Iris (anatomy)', 'start_paragraph_id': 3, 'start_character': 70, 'end_paragraph_id': 3, 'end_character': 76, 'bleu_score': 1.0, 'section': 'Section::::Structure.\n'}]}, {'answer': 'epithelial cells', 'provenance': [{'wikipedia_id': '86801', 'title': 'Iris (anatomy)', 'start_paragraph_id': 3, 'start_character': 112, 'end_paragraph_id': 3, 'end_character': 128, 'bleu_score': 1.0, 'section': 'Section::::Structure.\n'}]}, {'provenance': [{'wikipedia_id': '86801', 'title': 'Iris (anatomy)', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 128, 'bleu_score': 0.7848518349390631, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6308621029086988080}, 'section': 'Section::::Structure.\n'}]}]