code: function renderToString(element) {
    !ReactElement.isValidElement(element) ? "development" !== 'production' ? invariant(false, 'renderToString(): You must pass a valid ReactElement.') : _prodInvariant('46') : void 0;
    return renderToStringImpl(element, false);
  }
docs: Render a ReactElement to its initial HTML. This should only be used on the
  server.
  See https://facebook.github.io/react/docs/top-level-api.html#reactdomserver.rendertostring