old_contents: import os
  import tornado.web
  from loadsbroker.webapp.api import RootHandler, RunHandler
  from loadsbroker.webapp.views import GrafanaHandler
  
  
  _GRAFANA = os.path.join(os.path.dirname(__file__), 'grafana')
  
  
  application = tornado.web.Application([
      (r"/api", RootHandler),
      (r"/api/run/(.*)", RunHandler),
      (r"/dashboards/run/(.*)", GrafanaHandler, {"path": _GRAFANA})
  ])
  
new_contents: import os
  import tornado.web
  from loadsbroker.webapp.api import RootHandler, RunHandler
  from loadsbroker.webapp.views import GrafanaHandler
  
  
  _GRAFANA = os.path.join(os.path.dirname(__file__), 'grafana')
  
  
  application = tornado.web.Application([
      (r"/api", RootHandler),
      (r"/api/run/(.*)", RunHandler),
      (r"/dashboards/run/(.*)", GrafanaHandler, {"path": _GRAFANA, "default_filename": "index.html"})
  ])
  
subject: Set the `default_filename` for `GrafanaHandler`.