@Override
    public Mono<Void> setTransactionIsolationLevel(IsolationLevel isolationLevel) {
        return Mono.error(new UnsupportedOperationException("Transaction isolation level can not be changed."));
    }
Since transactions are not supported, this method will throw exception.

@param isolationLevel isolation level for transaction
clickhouse-r2dbc/src/main/java/com/clickhouse/r2dbc/connection/ClickHouseConnection.java