The _Railplus_ topic provides a topic specifically for iframe use.

```jsx
import React, { useMemo, useState, useEffect } from "react";
import {
  TextField,
  FormControl,
  Select,
  InputLabel,
  MenuItem,
} from "@mui/material";
import Editor from "react-styleguidist/lib/client/rsg-components/Editor";
import Heading from "react-styleguidist/lib/client/rsg-components/Heading";
import DocForm from "../../DocForm";
import getIframeCodeFromUrl from "../getIframeCodeFromUrl";
import getHtmlPageCode from "../getHtmlPageCode";
import iframeSearchParams from "../iframeSearchParams";
import { PDF_DOWNLOAD_EVENT_TYPE } from "../../../utils/constants";
// The `apiKey` used here is for demonstration purposes only.
// Please get your own api key at https://developer.geops.io/.
const apiKey = window.apiKey;
const baseUrl = "https://maps.trafimage.ch";
const topic = "ch.railplus.mitglieder";

const extraCode = `
    <button onclick="downloadPdf()" style="margin: 10px 5px; padding: 10px 5px">Export PDF</button>
    <script>
      function downloadPdf() {
        const iframe = document.getElementsByTagName('iframe');
        if (iframe) {
          iframe.contentWindow.postMessage('${PDF_DOWNLOAD_EVENT_TYPE}', '*');
        }
      }
    </script>`;

const App = () => {
  const [url, setUrl] = useState(baseUrl + "/" + topic + "?lang=de");
  const code = getHtmlPageCode(getIframeCodeFromUrl(`${url}`), extraCode);

  return (
    <>
      <div className="container">
        <iframe src={url} id="railplus-iframe" />
      </div>
      <button
        style={{ margin: "10px 5px", padding: "10px 5px" }}
        onClick={() => {
          const iframe = document.getElementById("railplus-iframe");
          if (iframe) {
            iframe.contentWindow.postMessage(PDF_DOWNLOAD_EVENT_TYPE, "*");
          }
        }}
      >
        Export PDF
      </button>
      <br />
      <Editor
        code={code}
        onChange={(code) => null} //setCode(code)}
      />
      <br />
      <DocForm
        value={url}
        onChange={(newUrl) => {
          setUrl(newUrl);
        }}
        isIframe
        propConfig={iframeSearchParams}
        filter={(config) => ["lang"].includes(config.name)}
      />
    </>
  );
};

<App />;
```
