Function keyed 

pub fn keyed<Factory, Selector, Role, W, P, Rejection, Source, Diagnostics, Key, Job, WorkerResult>(
    factory: Factory,
    roles: OrderedRoles<Role>,
    selector: Selector,
    activation: ActivationPolicy,
    recovery: PoolRecovery<Source>,
    backlog: BacklogCapacity,
    binding_capacity: BindingCapacity,
    interruption: Interruption,
    actor_drain: ActorDrainPolicy,
    diagnostics: DiagnosticDisposition<Diagnostics>,
) -> Result<KeyedPool<Role, W, P, Source, Selector, Diagnostics, Key, Job, WorkerResult>, KeyedConstructionRejected<Factory, Selector, Role, W, P, Rejection, Source, Diagnostics>>
where
    Factory: FnMut(&Role) -> Result<WorkerSubmission<W, P>, Rejection>,
    Selector: Fn(&Key) -> Role,
    Role: Eq,
    W: Behavior,
    W::Protocol: Protocol<Msg = Assignment<Job>>,
    W::Sends: CompletesAssignments<WorkerResult = WorkerResult>,
    BehaviorAddr<W>: EndpointAddress,

Construct one keyed pool after preparing every declared worker in order.