Type Alias SlotSupply 

pub type SlotSupply = BTreeMap<String, Option<String>>;

What a host says about each slot, keyed by slot name.

Some(variant) renders that variant; None removes the slot because its present_when does not hold; a name absent from the map means the host has no opinion and the declared default is used.

A plain table rather than a callback, so what the model was told is decided before the run rather than during it: it can be recorded, compared and fingerprinted.

Aliased Type

pub struct SlotSupply { /* private fields */ }