Function map_reduce 

pub async fn map_reduce<I, T, F, Fut>(
    items: Vec<I>,
    options: ParallelOptions,
    f: F,
) -> Result<ParallelOutcome<T>>
where
    F: Fn(usize, I) -> Fut,
    Fut: Future<Output = Result<T>>,

Runs f over items concurrently (bounded by ParallelOptions::max_concurrency), collecting per-item outcomes in input order and applying the configured FailurePolicy.

f receives each item’s input index and the item, and returns a future yielding Result<T>. The mapping is deterministic in input order regardless of completion order.

Errors

• FailurePolicy::FailFast returns the first item error (in input order), cancelling remaining in-flight work.
• FailurePolicy::Quorum returns TinyAgentsError::Graph when fewer than the required number of items succeeded.
• FailurePolicy::CollectAll and FailurePolicy::BestEffort never error.