Teacher: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
Teacher: Now, understand the problem? Solve this instance: customer: Hi. I am Amy Lopez. 
 agent: Hello, how can I assist you? 
 customer: Can you help me in booking from PHL to DFW? 
 agent: Sure, may I know your preferable dates to travel? 
 customer: My travelling dates are 07/09 to 07/11. 
 agent: Sorry for the inconvenience, there is no flight available on your requested dates. 
 customer: No issue, thank you. 
 agent: You are welcome.
Student:
no_flight