code: function getImmediateCustomParent(tag) {
        var ptag = tag;
        while (ptag.__.isAnonymous) {
          if (!ptag.parent) { break }
          ptag = ptag.parent;
        }
        return ptag
      }
docs: Loop backward all the parents tree to detect the first custom parent tag
  @param   { Object } tag - a Tag instance
  @returns { Object } the instance of the first custom parent tag found