Function collect_hashes 

pub async fn collect_hashes<S: Store>(
    tree: &HashTree<S>,
    root: &Cid,
    concurrency: usize,
) -> Result<HashSet<Hash>, HashTreeError>

Collect all hashes in a tree using parallel traversal

This walks the tree and collects all unique hashes (both tree nodes and blobs). Uses parallel fetching for efficiency.

Arguments

• tree - The HashTree instance with store access
• root - Root CID to start from
• concurrency - Number of concurrent fetches

Returns

Set of all hashes in the tree