code: def html_visit_inheritance_diagram(self, node):
      # type: (nodes.NodeVisitor, inheritance_diagram) -> None
      
      graph = node['graph']
  
      graph_hash = get_graph_hash(node)
      name = 'inheritance%s' % graph_hash
  
      # Create a mapping from fully-qualified class names to URLs.
      graphviz_output_format = self.builder.env.config.graphviz_output_format.upper()
      current_filename = self.builder.current_docname + self.builder.out_suffix
      urls = {}
      for child in node:
          if child.get('refuri') is not None:
              if graphviz_output_format == 'SVG':
                  urls[child['reftitle']] = os.path.join("..", child.get('refuri'))
              else:
                  urls[child['reftitle']] = child.get('refuri')
          elif child.get('refid') is not None:
              if graphviz_output_format == 'SVG':
                  urls[child['reftitle']] = os.path.join('..', current_filename + '#' + child.get('refid'))
              else:
                  urls[child['reftitle']] = '#' + child.get('refid')
  
      dotcode = graph.generate_dot(name, urls, env=self.builder.env)
      render_dot_html(
          self, node, dotcode, {}, 'inheritance', 'inheritance',
          alt='Inheritance diagram of ' + node['content'],
          link_to_svg='<i class="fa fa-external-link" aria-hidden="true"></i>'' SVG')
      raise nodes.SkipNode
docs: Output the graph for HTML.  This will insert a PNG with clickable
      image map.