code: @Nonnull
    @ReturnsMutableCopy
    public static ICommonsList <IHCNode> getAsFlattenedList (@Nullable final IHCNode aNode)
    {
      final ICommonsList <IHCNode> ret = new CommonsArrayList <> ();
      _recursiveAddFlattened (aNode, ret);
      return ret;
    }
docs: Inline all contained node lists so that a "flat" list results. This only
  flattens something if the passed node is an
  {@link com.helger.html.hc.impl.HCNodeList} and all node-lists directly
  contained in the other node lists. Node-lists that are hidden deep inside the
  tree are not considered!
  
  @param aNode
  The source node. May be <code>null</code>.
  @return A non-<code>null</code> flattened list.