code: @Nullable
    public static Element getFirstChildElement (@Nullable final Node aStartNode)
    {
      if (aStartNode == null)
        return null;
      return NodeListIterator.createChildNodeIterator (aStartNode)
                             .findFirstMapped (filterNodeIsElement (), x -> (Element) x);
    }
docs: Get the first direct child element of the passed element.
  
  @param aStartNode
  The element to start searching. May be <code>null</code>.
  @return <code>null</code> if the passed element does not have any direct
  child element.