[April] went to the store with her sister [Ann]. Later that day, [April] had tea with her sister [Janet].
('Janet', 'Ann')
[April] went to the store with her sister [Ann]. Later that day, [April] had tea with her sister [Janet].
[{('Janet', 'sister', 'Ann'): [('Janet', 'sister', 'April'), ('April', 'sister', 'Ann')]}]
['sister', 'sister']