[{'role': 'USR', 'utterance': 'Can I help you?'}
 {'role': 'SYS', 'utterance': 'Yes. How much are these T-shirts?'}
 {'role': 'USR', 'utterance': 'They are 12 dollars 50 cents each.'}
 {'role': 'SYS', 'utterance': "I like the green one, but it isn't big enough. Have you got a larger size?"}
 {'role': 'USR', 'utterance': "Just a minute. No. I'm sorry. We haven't. What about the black one?"}
 {'role': 'SYS', 'utterance': "No, it's too dark. I prefer something lighter, yellow or pink."}
 {'role': 'USR', 'utterance': 'How about the pink one?'}]
{'role': 'SYS', 'utterance': "Yes, that's nice. I'll take it."}