You've created a program that plays a cities game with a user. The program needs to remember and update the user's current city. The code provided attempts to achieve this, but it has a scope issue.
As it stands, this code will raise an error because the variable user_city is not accessible outside the change_city function.
Add exactly one line of code inside the change_city function to fix this scope issue. The line should be added where the comment indicates. Do not modify any other part of the existing code.
