pub unsafe extern "C" fn coap_new_client_session_pki(
    ctx: *mut coap_context_t,
    local_if: *const coap_address_t,
    server: *const coap_address_t,
    proto: coap_proto_t,
    setup_data: *mut coap_dtls_pki_t
) -> *mut coap_session_t