user_query: Create Pets list.
response_text: Alright, I made a list called "Pets".
user_query: Add cat, dog and hamster to Pets list.
response_text: Sure. Cat, dog and hamster on your list called "Pets". Anything else?
User: How much was my cell phone bill this month no last month?
Parse: Get_bill ( account_type « cell phone » billing_date_span « last month » )