In this task, you are given a conversation between a flight agent and the customer. You are given 4 options and you need to select the goal of the conversation. It is provided as part of customer's context, which has to be one of the following: `book`: Make a new reservation, `cancel`: Cancel an existing reservation, `no_flight`: No flight found for the customer's preference, `no_reservation`: No reservation / No change / No cancellation was made in the conversation, mostly enquiring details

customer: Hi. 
 agent: Hello. 
 customer: I am Rachel Lee. 
 agent: How may I serve you? 
 customer: I want to change my reservation, can you help me? 
 agent: Sure, I will help you with the change of flight reservation. 
 customer: Ok. 
 agent: Please wait for a moment. 
 customer: Sure. 
 agent: Thanks for waiting. But I am sorry to say that there is no flight reservation on your name to change it. 
 customer: That's ok. Thank you for your help. 
 agent: Thank you.
no_reservation