Depending on if child is null, either wraps child inside of a
maybe container or creates a Nothing instance for the given type.
At least one of child_type and child must be non-null.
If child_type is non-null then it must be a definite type.
If they are both non-null then child_type must be the type
of child.
Depending on if child is null, either wraps child inside of a maybe container or creates a Nothing instance for the given type.
At least one of child_type and child must be non-null. If child_type is non-null then it must be a definite type. If they are both non-null then child_type must be the type of child.
If child is a floating reference (see glib.variant.VariantG.refSink), the new instance takes ownership of child.