Function apply_slots 

pub fn apply_slots(
    raw: &str,
    resolved: &HashMap<String, Option<String>>,
    scope: &str,
) -> Result<String, DispatchError>

Apply an already-resolved scope to one piece of prompt text.

A slot resolved to None leaves nothing behind — deliberately the empty string rather than any variant, since the point of a condition that does not hold is that the wording must not appear.