a GLib.Variant created with g_icon_serialize()
Generate a Gio.Icon instance from str. This function can fail if
str is not valid - see g_icon_to_string() for discussion.
If your application or library provides one or more Gio.Icon
implementations you need to ensure that each GObject.GType is registered
with the type system prior to calling g_icon_new_for_string().
A string obtained via g_icon_to_string().
Deserializes a Gio.Icon previously serialized using
g_icon_serialize().