Question: who sings the theme song for touched by an angel
[{'answer': 'Della Reese', 'provenance': [{'wikipedia_id': '510590', 'title': 'Touched by an Angel', 'start_paragraph_id': 1, 'start_character': 327, 'end_paragraph_id': 1, 'end_character': 338, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '510590', 'title': 'Touched by an Angel', 'start_paragraph_id': 66, 'start_character': 0, 'end_paragraph_id': 66, 'end_character': 110, 'bleu_score': 0.910879922930628, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 16715273102785296164}, 'section': 'Section::::Production.:Theme song.\n'}]}]