Question: who are the main characters in the one and only ivan
[{'answer': 'Ivan', 'provenance': [{'wikipedia_id': '38525240', 'title': 'The One and Only Ivan', 'start_paragraph_id': 0, 'start_character': 17, 'end_paragraph_id': 0, 'end_character': 21, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Stella', 'provenance': [{'wikipedia_id': '38525240', 'title': 'The One and Only Ivan', 'start_paragraph_id': 3, 'start_character': 348, 'end_paragraph_id': 3, 'end_character': 354, 'bleu_score': 1.0, 'section': 'Section::::Plot.\n'}]}, {'answer': 'Bob', 'provenance': [{'wikipedia_id': '38525240', 'title': 'The One and Only Ivan', 'start_paragraph_id': 3, 'start_character': 373, 'end_paragraph_id': 3, 'end_character': 376, 'bleu_score': 1.0, 'section': 'Section::::Plot.\n'}]}, {'answer': 'Mack', 'provenance': [{'wikipedia_id': '38525240', 'title': 'The One and Only Ivan', 'start_paragraph_id': 4, 'start_character': 556, 'end_paragraph_id': 4, 'end_character': 560, 'bleu_score': 1.0, 'section': 'Section::::Plot.\n'}]}, {'answer': 'George', 'provenance': [{'wikipedia_id': '38525240', 'title': 'The One and Only Ivan', 'start_paragraph_id': 5, 'start_character': 276, 'end_paragraph_id': 5, 'end_character': 282, 'bleu_score': 1.0, 'section': 'Section::::Plot.\n'}]}, {'answer': 'Julia', 'provenance': [{'wikipedia_id': '38525240', 'title': 'The One and Only Ivan', 'start_paragraph_id': 5, 'start_character': 5, 'end_paragraph_id': 5, 'end_character': 10, 'bleu_score': 1.0, 'section': 'Section::::Plot.\n'}]}, {'answer': 'Ruby', 'provenance': [{'wikipedia_id': '38525240', 'title': 'The One and Only Ivan', 'start_paragraph_id': 4, 'start_character': 5, 'end_paragraph_id': 4, 'end_character': 9, 'bleu_score': 1.0, 'section': 'Section::::Plot.\n'}]}]