code: public WebElement locateElement(int index, String childLocator) {
          if (index < 0) {
              throw new IllegalArgumentException("index cannot be a negative value");
          }
          setIndex(index);
          WebElement locatedElement = null;
          if (getParent() != null) {
              locatedElement = getParent().locateChildElement(childLocator);
          } else {
              locatedElement = HtmlElementUtils.locateElement(childLocator, this);
          }
          return locatedElement;
      }
docs: Sets the container index and searches for the descendant element using the child locator.
  
  @param index
  index of the container element to search on
  @param childLocator
  locator of the child element within the container
  @return child WebElement found using child locator at the indexed container