python dict to json and sending to HTML using Flask

I need to print a big python dictionary in HTML with neat format to read using Flask.

Lets take this dict as example:

a={'a':True, 'b':False}
a_json=json.dumps(a) # {"a": true, "b": false}
return render_template("index.html", a_json=a_json)

In HTML:

  <div class="w3-container">
      <pre id="dict"></pre>
  </div>

  <script>
    var data = {{a_json}}
    document.getElementById("dict").innerHTML = JSON.stringify(data, undefined, 2);
  </script>

This does not showing the data, when I checked the open the "view page source", I see that the JSON data is different, and there are extra characters are available like this:

When, I give the JSON data directly in the script tag, I got the dictionary visible in the web page.

How to make this JSON data visible in the web page (or)
How to make the dict visible in html in neat format?

Thanks

Change the line

var data = {{a_json}}

to

var data = {{ a_json | safe }}

See https://stackoverflow.com/questions/3206344/passing-html-to-template-using-flask-jinja2