static Template parsedTemplateForResource(String resourceName) {
    try {
      return Template.parseFrom(resourceName, TemplateVars::readerFromUrl);
    } catch (IOException e) {
      throw new UncheckedIOException(e);
    }
  }
Returns the result of substituting the variables defined by the fields of this class (a
concrete subclass of TemplateVars) into the template returned by {@link #parsedTemplate()}.
value/src/main/java/com/google/auto/value/processor/TemplateVars.java