landmarkItem(item) {
    let content = Object(core["filterChildren"])(item, "a", true);

    if (!content) {
      return;
    }

    let type = content.getAttributeNS("http://www.idpf.org/2007/ops", "type") || undefined;
    let href = content.getAttribute("href") || "";
    let text = content.textContent || "";
    return {
      "href": href,
      "label": text,
      "type": type
    };
  }
Create a landmarkItem
@private
@param  {element} item
@return {object} landmarkItem