code: function (data) {
      if (data.src.tagName) {
        // Since `data.src` can be an element, parse out the string if necessary for the hash.
        data = utils.extendDeep({}, data);
        data.src = data.src.src;
      }
      return JSON.stringify(data);
    }
docs: Create a hash of the material properties for texture cache key.