jupyterlab/dev_mode/templates/partial.html

  <script id="jupyter-config-data" type="application/json">{
    {% for key, value in page_config.items() -%}
    "{{ key }}": "{{ value }}",
    {% endfor -%}
    "baseUrl": "{{ base_url }}",
    "wsUrl": "{{ ws_url }}"
  }</script>

  {% block favicon %}
  <link rel="icon" type="image/x-icon" href="{{ base_url }}static/base/images/favicon.ico" class="idle favicon">
  <link rel="" type="image/x-icon" href="{{ base_url }}static/base/images/favicon-busy-1.ico" class="busy favicon">
  {% endblock %}