code: @Nonnull
    public TypeaheadDataset setHeader (@Nullable final IHCNode aHeader)
    {
      return setHeader (aHeader != null ? HCRenderer.getAsHTMLStringWithoutNamespaces (aHeader) : (String) null);
    }
docs: The header rendered before suggestions in the dropdown menu. Can be either
  a DOM element or HTML.
  
  @param aHeader
  The header to use. May be <code>null</code>.
  @return this