Function nm_client_dbus_call 

pub unsafe extern "C" fn nm_client_dbus_call(
    client: *mut NMClient,
    object_path: *const c_char,
    interface_name: *const c_char,
    method_name: *const c_char,
    parameters: *mut GVariant,
    reply_type: *const GVariantType,
    timeout_msec: c_int,
    cancellable: *mut GCancellable,
    callback: GAsyncReadyCallback,
    user_data: gpointer,
)

Available on crate feature v1_24 only.