old_contents: import os
  
  from traitlets import default
  
  from .labapp import LabApp
  
  try:
      from jupyterhub.singleuser import SingleUserNotebookApp
  except ImportError:
      SingleUserLabApp = None
      raise ImportError('You must have jupyterhub installed for this to work.')
  else:
      class SingleUserLabApp(SingleUserNotebookApp, LabApp):
  
          @default("default_url")
          def _default_url(self):
              """when using jupyter-labhub, jupyterlab is default ui"""
              return "/lab"
  
          def init_webapp(self, *args, **kwargs):
               warnings.warn(
                  "SingleUserLabApp is deprecated, use SingleUserNotebookApp and set " + "c.Spawner.default_url = '/lab' in jupyterhub_config.py", DeprecationWarning
              )
              super().init_webapp(*args, **kwargs)
  
  
  def main(argv=None):
      return SingleUserLabApp.launch_instance(argv)
  
  
  if __name__ == "__main__":
      main()
  
new_contents: import os
  import warnings
  
  from traitlets import default
  
  from .labapp import LabApp
  
  try:
      from jupyterhub.singleuser import SingleUserNotebookApp
  except ImportError:
      SingleUserLabApp = None
      raise ImportError('You must have jupyterhub installed for this to work.')
  else:
      class SingleUserLabApp(SingleUserNotebookApp, LabApp):
  
          @default("default_url")
          def _default_url(self):
              """when using jupyter-labhub, jupyterlab is default ui"""
              return "/lab"
  
          def init_webapp(self, *args, **kwargs):
              warnings.warn(
                  "SingleUserLabApp is deprecated, use SingleUserNotebookApp and set " + \
                  "c.Spawner.default_url = '/lab' in jupyterhub_config.py", DeprecationWarning
              )
              super().init_webapp(*args, **kwargs)
  
  
  def main(argv=None):
      return SingleUserLabApp.launch_instance(argv)
  
  
  if __name__ == "__main__":
      main()
  
subject: Fix LabHubApp.