How many senators have read "Green eggs and ham" on the senate floor?
{'directed': True, 'multigraph': False, 'graph': {}, 'nodes': [{'type': 'INTERNAL', 'name_': 'Q30', 'id': 0, 'label': 'United States of America'}, {'type': 'INTERNAL', 'name_': 'Q36180', 'id': 1, 'label': 'writer'}, {'type': 'INTERNAL', 'name_': 'Q12737077', 'id': 2, 'label': 'occupation'}, {'type': 'QUESTIONS_ENTITY', 'name_': 'Q4416090', 'id': 3, 'label': 'United States senator'}, {'type': 'INTERNAL', 'name_': 'Q298685', 'id': 4, 'label': 'Dr. Seuss'}, {'type': 'ANSWER_CANDIDATE_ENTITY', 'name_': 'Q15686806', 'id': 5, 'label': 'senator'}, {'type': 'QUESTIONS_ENTITY', 'name_': 'Q2759523', 'id': 6, 'label': 'Green Eggs and Ham'}], 'links': [{'name_': 'P17', 'source': 0, 'target': 0, 'label': 'country'}, {'name_': 'P31', 'source': 1, 'target': 2, 'label': 'instance of'}, {'name_': 'P17', 'source': 3, 'target': 0, 'label': 'country'}, {'name_': 'P279', 'source': 3, 'target': 5, 'label': 'subclass of'}, {'name_': 'P27', 'source': 4, 'target': 0, 'label': 'country of citizenship'}, {'name_': 'P106', 'source': 4, 'target': 1, 'label': 'occupation'}, {'name_': 'P800', 'source': 4, 'target': 6, 'label': 'notable work'}, {'name_': 'P31', 'source': 5, 'target': 2, 'label': 'instance of'}]}