Which widow was elected to fill her dead husband's senate seat who also became the first woman to serve in both chambers of Congress?
{'directed': True, 'multigraph': False, 'graph': {}, 'nodes': [{'type': 'INTERNAL', 'name_': 'Q4167836', 'id': 0, 'label': 'Wikimedia category'}, {'type': 'QUESTIONS_ENTITY', 'name_': 'Q11268', 'id': 1, 'label': 'United States Congress'}, {'type': 'QUESTIONS_ENTITY', 'name_': 'Q66096', 'id': 2, 'label': 'United States Senate'}, {'type': 'INTERNAL', 'name_': 'Q105411798', 'id': 3, 'label': 'Category:Majority leaders of the United States Senate'}, {'type': 'ANSWER_CANDIDATE_ENTITY', 'name_': 'Q28530268', 'id': 4, 'label': 'Majority Leader of the United States Senate'}, {'type': 'INTERNAL', 'name_': 'Q8871766', 'id': 5, 'label': 'Category:United States Senate'}, {'type': 'INTERNAL', 'name_': 'Q6441213', 'id': 6, 'label': 'Category:United States Congresses'}], 'links': [{'name_': 'P527', 'source': 1, 'target': 2, 'label': 'has part(s)'}, {'name_': 'P31', 'source': 3, 'target': 0, 'label': 'instance of'}, {'name_': 'P301', 'source': 3, 'target': 4, 'label': "category's main topic"}, {'name_': 'P31', 'source': 5, 'target': 0, 'label': 'instance of'}, {'name_': 'P301', 'source': 5, 'target': 2, 'label': "category's main topic"}, {'name_': 'P31', 'source': 6, 'target': 0, 'label': 'instance of'}, {'name_': 'P301', 'source': 6, 'target': 1, 'label': "category's main topic"}]}