Function validate_space_index 

pub fn validate_space_index<S, A, Store, Props, R, Sch>(
    model: &StandardModel<S, A, Store, Props, R, Sch>,
) -> Result<(), InteractionError<S::Error>>
where
    A: PositionedAgent,
    S: SpaceInteraction<A>,
    Store: AgentStore<A>,
    R: RngCore,
    Sch: Scheduler<StandardModel<S, A, Store, Props, R, Sch>>,

Validate that every positioned agent in the store is present exactly once in the spatial index at its stored position.