ID is not parsing in attributes

[rohanashik]

Example:

Mardown table:

## Table of Contents
- [Introduction](#introduction)
  - [Subtopic 1](#subtopic-1)
  - [Subtopic 2](#subtopic-2)
- [Main Content](#main-content)
  - [Chapter 1](#chapter-1)
    - [Section 1.1](#section-11)
    - [Section 1.2](#section-12)
  - [Chapter 2](#chapter-2)
- [Conclusion](#conclusion)

The above should be pointing to the corresponding heading:

# Introduction
## Subtopic 1
## Subtopic 2
# Main Content
## Chapter 1
### Section 1.1
### Section 1.2
## Chapter 2
# Conclusion

Output should be:

<h2>Table of Contents</h2>
<ul>
  <li><a href="#introduction">Introduction</a>
    <ul>
      <li><a href="#subtopic-1">Subtopic 1</a></li>
      <li><a href="#subtopic-2">Subtopic 2</a></li>
    </ul>
  </li>
  <li><a href="#main-content">Main Content</a>
    <ul>
      <li><a href="#chapter-1">Chapter 1</a>
        <ul>
          <li><a href="#section-11">Section 1.1</a></li>
          <li><a href="#section-12">Section 1.2</a></li>
        </ul>
      </li>
      <li><a href="#chapter-2">Chapter 2</a></li>
    </ul>
  </li>
  <li><a href="#conclusion">Conclusion</a></li>
</ul>

<h1 id="introduction">Introduction</h1>
<h2 id="subtopic-1">Subtopic 1</h2>
<h2 id="subtopic-2">Subtopic 2</h2>
<h1 id="main-content">Main Content</h1>
<h2 id="chapter-1">Chapter 1</h2>
<h3 id="section-11">Section 1.1</h3>
<h3 id="section-12">Section 1.2</h3>
<h2 id="chapter-2">Chapter 2</h2>
<h1 id="conclusion">Conclusion</h1>

But the id is not parsed in the django template. Even added the ID in whitelisting

        "WHITELIST_ATTRS": [
            'href',
            'src',
            'alt',
            'class',
            'id'
        ],

[erwinmatijsen]

If you add "markdown.extensions.toc" to MARKDOWN_EXTENSIONS, it will work. See the docs about extensions.