pub fn commit<T: pristine::MutTxnT>(txn: std::sync::Arc<std::sync::RwLock<T>>) -> Result<(), T::GraphError> {
    let txn = if let Ok(txn) = std::sync::Arc::try_unwrap(txn) {
        txn.into_inner().unwrap()
    } else {
        unreachable!()
    };
    txn.commit()
}