protected Element getChildElement(int index) {
        Element childContainer = getChildContainer();
        int childCount = childContainer.getChildCount();
        return (index < childCount) ? childContainer.getChild(index).<Element> cast() : null;
    }
Get the element that represents the specified index.

@param index the index of the row value
@return the child element, or null if it does not exist
stroom-core-client-widget/src/main/java/com/google/gwt/user/cellview/client/AbstractHasData.java