docs: def download_file(filename: str):
      """ downloads the specified project file if it exists """
  
      project = cd.project.get_internal_project()
      source_directory = project.source_directory if project else None
  
      if not filename or not project or not source_directory:
          return '', 204
  
      path = os.path.realpath(os.path.join(
          source_directory,
          '..',
          '__cauldron_downloads',
          filename
      ))
  
      if not os.path.exists(path):
          return '', 204
  
      return flask.send_file(path, mimetype=mimetypes.guess_type(path)[0])