user_query: create a grocery list and add celery, tomato, buns, ketchup, mayo to the list
response_text: Sorry, it looks like you already have a list with that name. Do you still want to make a new one?
user_query: yes
response_text: Sure, I made a list called "Grocery" and added those three things.
User: Stop this walk, I mean the run.
Parse: Stop_exercise ( activity « walk » activity « run » )