[{'role': 'USR', 'utterance': 'Lily, do you know Lizzy?'}
 {'role': 'SYS', 'utterance': 'Lizzy who?'}
 {'role': 'USR', 'utterance': 'Lizzy smith.'}
 {'role': 'SYS', 'utterance': 'Of course I do.'}
 {'role': 'USR', 'utterance': 'Then, Do you know her younger sister?'}
 {'role': 'SYS', 'utterance': 'You mean Mary?'}
 {'role': 'USR', 'utterance': 'Yes.'}]
{'role': 'SYS', 'utterance': 'Sure. I know her elder sister Sue and younger sister Mary.'}