docs: public void close()
      {
          if (transac_open)
          {
              try
              {
                  this._cnx.rollback();
              }
              catch (Exception e)
              {
                  // Ignore.
              }
          }
  
          for (Statement s : toClose)
          {
              closeQuietly(s);
          }
          toClose.clear();
  
          closeQuietly(_cnx);
          _cnx = null;
      }