renderSafeStyleSheet(template, templateData = undefined) {
    const result = this.renderStrictOfKind(
        template, templateData, SanitizedContentKind.CSS);
    return result.toSafeStyleSheet();
  }
Renders a strict Soy template of kind="css" and returns the result as
a SafeStyleSheet object.
Rendering a template that is not a strict template of kind="css" results in
a runtime and compile-time error.
@param {function(ARG_TYPES, ?Object<string, *>=):
    !SanitizedCss} template The Soy template to render.
@param {ARG_TYPES=} templateData The data for the template.
@return {!SafeStyleSheet}
@template ARG_TYPES