docs: public T extractFromPayload(String path, String variable) {
          if (JsonPathMessageValidationContext.isJsonPathExpression(path)) {
              getJsonPathVariableExtractor().getJsonPathExpressions().put(path, variable);
          } else {
              getXpathVariableExtractor().getXpathExpressions().put(path, variable);
          }
          return self;
      }