docs: static private Result parseBooleanResult(Command cmd, XMLStreamReader rdr, 
        List<String> metadata) throws XMLStreamException, SparqlException {
      if (rdr.next() != CHARACTERS) {
        throw new SparqlException("Unexpected data in Boolean result: " + rdr.getEventType());
      }
      boolean result = Boolean.parseBoolean(rdr.getText());
      testClose(rdr, rdr.nextTag(), BOOLEAN, "Bad close of boolean element");
      cleanup(rdr);
      return new ProtocolBooleanResult(cmd, result, metadata);
    }