Question: who was tupac a back up dancer for
[{'answer': 'Digital Underground', 'provenance': [{'wikipedia_id': '31341', 'title': 'Tupac Shakur', 'start_paragraph_id': 16, 'start_character': 278, 'end_paragraph_id': 16, 'end_character': 297, 'bleu_score': 1.0, 'section': 'Section::::Early life.:Move to California.\n'}]}, {'provenance': [{'wikipedia_id': '31341', 'title': 'Tupac Shakur', 'start_paragraph_id': 16, 'start_character': 0, 'end_paragraph_id': 16, 'end_character': 305, 'bleu_score': 0.915132941383415, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 697500642928975311}, 'section': 'Section::::Early life.:Move to California.\n'}]}]