[Nancy] asked her father [Clarence] if she could spend the night at her friend's house. [Nancy] picked up her daughter [Heidi] from school early.
('Heidi', 'Clarence')
[Nancy] picked up her daughter [Heidi] from school early. [Nancy] asked her father [Clarence] if she could spend the night at her friend's house.
[{('Heidi', 'grandfather', 'Clarence'): [('Heidi', 'mother', 'Nancy'), ('Nancy', 'father', 'Clarence')]}]
['mother', 'father']