First the iterator is advanced to the next (possibly first) attribute. If that fails, then false is returned and there are no other effects.
The value returned in
name remains valid for as long as the iterator remains at the current position. The value returned in
value must be unreffed using
g_variant_unref when it is no longer in use.
the type of the attribute
the attribute value
true on success, or false if there is no additional attribute