NULL_VALUE
NULL_VALUE
If you need to specify a NULL JSON value, use Google_Model::NULL_VALUE instead - it will be replaced when converting to JSON with a real null.
Extension to the regular Google_Model that automatically exposes the items array for iteration, so you can just iterate over the object rather than a reference inside.
http://tools.ietf.org/html/draft-zyp-json-schema-03#section-5