Function known_chain_ancestor_iter 

pub(crate) fn known_chain_ancestor_iter<Item>(
    chain: Option<Arc<Chain>>,
    db: &ZebraDb,
    hash_or_height: HashOrHeight,
) -> Iter<Item> 
where
    Item: ChainItem,

Returns a generic chain item iterator over a chain containing hash_or_height, in order from the largest height to genesis.

The item with hash_or_height is included in the iterator. hash_or_height must be in chain or db.