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: OK, I made a list called "Grocery" and added those three things.
user_query: erase ketchup from grocery list
response_text: I couldn't find ketchup on your list called "Grocery."
User: Purchase some tickets to the event.
Parse: BuyEventTickets ( )