[Vala] How to create functon that maps to D-Bus a{s(st)}?

["marcin saepia net" <marcin saepia net>]

Hi,

I see that if I create function with signature like

public void f(HashTable<string, Variant> arg)

and then export the object over D-Bus, Vala compiler automatically
generates its DBus signature of a{sv}. Great.

I need to achieve a{s(st)}, in other words, I need a hashmap with
strings as keys and structure that contains string and uint64 as a
value.

What signature should have function in vala to map in such way?

Thank you,

Marcin