Question: who is the actor that plays saul on grace and frankie
[{'answer': 'Sam Waterston', 'provenance': [{'wikipedia_id': '43696046', 'title': 'Grace and Frankie', 'start_paragraph_id': 1, 'start_character': 346, 'end_paragraph_id': 1, 'end_character': 359, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '43696046', 'title': 'Grace and Frankie', 'start_paragraph_id': 10, 'start_character': 0, 'end_paragraph_id': 10, 'end_character': 135, 'bleu_score': 0.9021315316859231, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 12800483491291787674}, 'section': 'Section::::Cast.:Main.\n'}]}, {'provenance': [{'wikipedia_id': '43696046', 'title': 'Grace and Frankie', 'section': 'Section::::Abstract.', 'start_paragraph_id': 1, 'end_paragraph_id': 1, 'meta': {'evidence_span': ['Sam Waterston, Martin Sheen, Brooklyn Decker, Ethan Embry, June Diane Raphael, and Baron Vaughn co-star in supporting roles.', 'Sam Waterston, Martin Sheen, Brooklyn Decker, Ethan Embry, June Diane Raphael, and Baron Vaughn co-star in supporting roles.']}}]}, {'provenance': [{'wikipedia_id': '43696046', 'title': 'Grace and Frankie', 'section': 'Section::::Cast.:Main.\n', 'start_paragraph_id': 10, 'start_character': 12, 'end_paragraph_id': 10, 'end_character': 42, 'bleu_score': 1.0}]}]