There are 133 trains. Where will you be leaving from?
I want a train going to stansted airport . I'm leaving from Cambridge.
{"__type": "Inform", "entity": {"__type": "Train", "choice": "133"}} {"__type": "Request", "service": "train", "values": ["departure"]}
{"__type": "Request", "service": "train", "values": ["arrive by", "day", "leave at"]}
And what day and time would you like to travel?