create_cart
Use this function to create a new shopping cart. Reservations created with the function 
make_reservation can then use this cart id to group reservations into a single cart.
 site_id int optional
If using a metasite API key and you want to create the cart on the site level, you can specify the site ID for which the shopping cart should be created. Otherwise leave this empty
 method string required
must be set to 
create_cart language string optional
by specifying a 2-letter (ISO 639-1) language code (all capital letters e.g. EN, DE, FR, ES, IT) you can change the language of the text values returned
 api_key string required
your API key - 
Click here to get your key. If your API key uses a hash key, you must also include the parameters 
hash_key and hash_timestamp.
 cart_id int
ID of the new cart
Click here to test this function in the API playground.