WPCOM_JSON_API_Endpoint::is_post_type_allowed PHP Method

    function is_post_type_allowed($post_type)
    {
        // if the post type is empty, that's fine, WordPress will default to post
        if (empty($post_type)) {
            return true;
        }
        // allow special 'any' type
        if ('any' == $post_type) {
            return true;
        }
        // check for allowed types
        if (in_array($post_type, $this->_get_whitelisted_post_types())) {
            return true;
        }
        return false;
    }