    def initialize_templates(self):
        """Patch classic-noteboook page templates to add Hub-related buttons"""

        app = self.serverapp

        jinja_template_vars = app.jinja_template_vars

        # override template vars
        jinja_template_vars['logo_url'] = self.hub_auth.hub_host + url_path_join(
            self.hub_auth.hub_prefix, 'logo'
        )
        jinja_template_vars['hub_control_panel_url'] = (
            self.hub_auth.hub_host + url_path_join(self.hub_auth.hub_prefix, 'home')
        )
Patch classic-noteboook page templates to add Hub-related buttons
jupyterhub/singleuser/extension.py