title: Template tags in django
body: <p>In djangobook in chapter 9 on advanced templates it shows how the <code>{% comment %}</code> tag is implemented. </p>
  
  <pre><code>def do_comment(parser, token):
      nodelist = parser.parse(('endcomment',))
      parser.delete_first_token()
      return CommentNode()
  
  class CommentNode(template.Node):
      def render(self, context):
          return ''
  </code></pre>
  
  <p>According to the book in the function <code>do_comment</code> after parser.parse() is called, the parser hasn’t yet “consumed” the <code>{% endcomment %}</code> tag, so the code needs to explicitly call parser.delete_first_token() to prevent that tag from being processed twice. Can anyone please explain what does that mean.</p>