Function buffer_hash_to_tx_fetcher 

pub fn buffer_hash_to_tx_fetcher(
    tx_fetcher: &mut TransactionFetcher,
    hash: FixedBytes<32>,
    peer_id: FixedBytes<64>,
    retries: u8,
    tx_encoded_length: Option<usize>,
)

Directly buffer hash into tx fetcher for testing.