parseSpine(spineXml, manifest) {
    var spine = [];
    var selected = Object(core["qsa"])(spineXml, "itemref");
    var items = Array.prototype.slice.call(selected); // var epubcfi = new EpubCFI();
    //-- Add to array to mantain ordering and cross reference with manifest

    items.forEach(function (item, index) {
      var idref = item.getAttribute("idref"); // var cfiBase = epubcfi.generateChapterComponent(spineNodeIndex, index, Id);

      var props = item.getAttribute("properties") || "";
      var propArray = props.length ? props.split(" ") : []; // var manifestProps = manifest[Id].properties;
      // var manifestPropArray = manifestProps.length ? manifestProps.split(" ") : [];

      var itemref = {
        "idref": idref,
        "linear": item.getAttribute("linear") || "yes",
        "properties": propArray,
        // "href" : manifest[Id].href,
        // "url" :  manifest[Id].url,
        "index": index // "cfiBase" : cfiBase

      };
      spine.push(itemref);
    });
    return spine;
  }
Parse Spine
@private
@param  {node} spineXml
@param  {Packaging.manifest} manifest
@return {object} spine