[Lynn] called [David], her sister, to see if she wanted to go out to eat. [Lena] took her younger sister [Lynn] to the carnival last weekend. [Cindy] was sewing a sweater for her sister [Lena].
('David', 'Cindy')
[Lynn] called [David], her sister, to see if she wanted to go out to eat. [Lena] took her younger sister [Lynn] to the carnival last weekend. [Cindy] was sewing a sweater for her sister [Lena].
[{('David', 'sister', 'Cindy'): [('David', 'sister', 'Lynn'), ('Lynn', 'sister', 'Cindy')]}, {('Lynn', 'sister', 'Cindy'): [('Lynn', 'sister', 'Lena'), ('Lena', 'sister', 'Cindy')]}]
['sister', 'sister', 'sister']