Question: who is the supreme justice of the supreme court
[{'answer': 'John Roberts', 'provenance': [{'wikipedia_id': '31739', 'title': 'Chief Justice of the United States', 'start_paragraph_id': 4, 'start_character': 155, 'end_paragraph_id': 4, 'end_character': 167, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '31739', 'title': 'Chief Justice of the United States', 'start_paragraph_id': 4, 'start_character': 0, 'end_paragraph_id': 4, 'end_character': 343, 'bleu_score': 0.530582438670381, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 11510295151575731709}, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '31739', 'title': 'Chief Justice of the United States', 'section': 'Section::::Abstract.', 'start_paragraph_id': 3, 'end_paragraph_id': 3, 'meta': {'evidence_span': ['The chief justice is also an "ex officio" member of the Board of Regents of the Smithsonian Institution and, by custom, is elected chancellor of the board. Since the Supreme Court was established in 1789, 17 people have served as chief justice, beginning with John Jay (17891795). The current chief justice is John Roberts (since 2005).', 'The current chief justice is John Roberts']}}]}, {'provenance': [{'wikipedia_id': '31739', 'title': 'Chief Justice of the United States', 'section': 'Section::::Abstract.', 'start_paragraph_id': 4, 'end_paragraph_id': 4, 'meta': {'evidence_span': ['Since the Supreme Court was established in 1789, 17 people have served as chief justice, beginning with John Jay (17891795). The current chief justice is John Roberts (since 2005). John Rutledge, Edward Douglass White, Charles Evans Hughes, Harlan Fiske Stone, and William Rehnquist served as associate justice prior to becoming chief justice.', 'Since the Supreme Court was established in 1789, 17 people have served as chief justice, beginning with John Jay (17891795). The current chief justice is John Roberts', 'The current chief justice is John Roberts']}}]}]