[Louise] and her sister [Linda] went to the basketball game. [Louise] invited [Robert] to meet them there, since she is his sister.
('Robert', 'Linda')
[Louise] and her sister [Linda] went to the basketball game. [Louise] invited [Robert] to meet them there, since she is his sister.
[{('Robert', 'sister', 'Linda'): [('Robert', 'sister', 'Louise'), ('Louise', 'sister', 'Linda')]}]
['sister', 'sister']