code: public String asset(String path) {
          Asset asset = assets.assetAt(path);
          if (asset == null) {
              // If the path starts with "/", try without
              if (path.startsWith("/")) {
                  return asset(path.substring(1));
              }
              // Not found.
              throw new TemplateProcessingException("Cannot find the URL of the asset " + path);
          }
          return asset.getPath();
      }
docs: Gets the url of the given asset. Throws an exception if the asset cannot be found.
  
  @param path the asset's path
  @return the url