Function read_prunable_tape 

pub fn read_prunable_tape(
    tx_id: &TxId,
    tx_info: &TxInfo,
    buf: &mut [u8],
    tapes: &impl TapesRead,
    db: &BlockchainDatabase,
) -> Result<(), BlockchainError>

Gets a transaction by reading the prunable_tape if it is Some or otherwise, checking the tip block if the tx is there

If it’s neither where, it errors.