docs: public synchronized void setTransactionIsolation(
              int level) throws SQLException {
  
          checkClosed();
  
          switch (level) {
  
              case TRANSACTION_READ_UNCOMMITTED :
              case TRANSACTION_READ_COMMITTED :
              case TRANSACTION_REPEATABLE_READ :
              case TRANSACTION_SERIALIZABLE :
                  break;
              default :
                  throw Util.invalidArgument();
          }
  
          try {
              sessionProxy.setIsolationDefault(level);
          } catch (HsqlException e) {
              throw Util.sqlException(e);
          }
      }