Function nearby_ids 

pub fn nearby_ids<S, A, Store, Props, R, Sch>(
    model: &StandardModel<S, A, Store, Props, R, Sch>,
    position: &A::Position,
    radius: usize,
) -> Vec<AgentId> 
where
    A: PositionedAgent,
    S: SpaceInteraction<A>,
    Store: AgentStore<A>,
    R: RngCore,
    Sch: Scheduler<StandardModel<S, A, Store, Props, R, Sch>>,

Query agent IDs near a position, using the space’s distance metric.

The meaning of radius depends on the space: grid cells (Chebyshev), Euclidean distance (continuous), or graph hops (graph).