code: private XpathPayloadVariableExtractor getXpathVariableExtractor() {
          if (xpathExtractor == null) {
              xpathExtractor = new XpathPayloadVariableExtractor();
  
              getAction().getVariableExtractors().add(xpathExtractor);
          }
  
          return xpathExtractor;
      }
docs: Creates new variable extractor and adds it to test action.