How should data be set for Sophia Map nesting

As the picture shows, there is a Map nested in the Map, should I set the data in, and update the data?

@hanssv.chain You know what?

I tried this, but it also reported an error

put(state{test["key"]["item"] = "value"}) is only correct if state.test["key"] is actually a map, otherwise it is impossible to insert "item" = "value" into it?!

The quickfix is to use a default value when a key is not present during an update:
put(state{test["key" = {}]["item"] = "value"})