code: function addPid(content) {
      var shapeReg = /<(path|rect|circle|polygon|line|polyline|ellipse)\s/gi;
      var id = 0;
      content = content.replace(shapeReg, function (match) {
          return match + ("pid=\"" + id++ + "\" ");
      });
      return content;
  }
docs: add pid attr, for css