docs: private void logRequest(ResultType cmdType, String mimeType) {
      StringBuilder sb = new StringBuilder("Executing SPARQL protocol request ");
      sb.append("to endpoint <").append(((ProtocolDataSource)getConnection().getDataSource()).getUrl()).append("> ");
      if (mimeType != null) {
        sb.append("for content type '").append(mimeType).append("' ");
      } else {
        sb.append("for unknown content type ");
      }
      if (cmdType != null) {
        sb.append("with expected results of type ").append(cmdType).append(".");
      } else {
        sb.append("with unknown expected result type.");
      }
      logger.debug(sb.toString());
    }