Sip Uri Header

[MoMannn]

sip:user:password@host:port;uri-parameters?headers

This is the standard sip uri but in doubango I can set everything except the headers, they are always removed and in the sip uri class:

typedef struct tsip_uri_s {
    TSK_DECLARE_OBJECT;

    tsip_uri_type_t type;
    char *scheme;
    char *host; /**< Host name. Hostname or IPv4address or IPv6address. */
    tsip_host_type_t host_type; /**< IPv4 or IPv6 or domain name. */
    uint16_t port;
    char *user_name;
    char *password;
    char *display_name;

    tsk_params_L_t *params; /**< list of @ref tsk_param_t elements containing all parameters. */
}

I don't see any definition for headers. How can I set them? Does doubango not support them?