docs: function fixUseElements(contentDocument) {
          // find all <use> elements
          var useEls = contentDocument.querySelectorAll('use');
          [].forEach.call(useEls, function (use) {
              var id = use.getAttribute('xlink:href'),
                  // clone the referenced <image> element
                  image = contentDocument.querySelector(id).cloneNode(),
                  parent = use.parentNode;
              // remove the id so we don't have duplicates
              image.removeAttribute('id');
              // copy over the transform
              image.setAttribute('transform', use.getAttribute('transform'));
              // replace the use with the image
              parent.replaceChild(image, use);
          });
      }