If the device if of type %GDK_DEVICE_TYPE_MASTER, it will return the list of slave devices attached to it, otherwise it will return %NULL
the list of slave devices, or %NULL. The list must be freed with g_list_free(), the contents of the list are owned by GTK+ and should not be freed.
See Implementation
If the device if of type %GDK_DEVICE_TYPE_MASTER, it will return the list of slave devices attached to it, otherwise it will return %NULL