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: Please add avocados to the shopping list.
Parse: Add_item_to_list ( items « avocados » list_label « shopping » list_singular_or_plural « list » )