code: def _is_user_directory(self, pathname):
        
        fullpath = os.path.join(self.userdata_location(), pathname)
        # SteamOS puts a directory named 'anonymous' in the userdata directory
        # by default. Since we assume that pathname is a userID, ignore any name
        # that can't be converted to a number
        return os.path.isdir(fullpath) and pathname.isdigit()
docs: Check whether `pathname` is a valid user data directory
  
        This method is meant to be called on the contents of the userdata dir.
        As such, it will return True when `pathname` refers to a directory name
        that can be interpreted as a users' userID.