Is it illegal to own a pig in the city of Chicago?

I am really interested in getting a teacup pig, but have heard that it is illegal to keep livestock in Chicago in residential areas. I have checked out the Municipal Codes for the city, but none seem to say that you can't own and keep a pig as a pet, and it says that any ownership of "wild animals" may require a license, and there is question of proper confinement of animals construed as dangerous. Something tells me a teacup pig wouldn't exactly be a threat to society. Any ideas?