code: def _setup_storage_dir(self):
          
          dir_path = self._settings.get(config.DIRECTORY)
          if dir_path is None:
              dir_path = self._default_path
              if not os.path.exists(dir_path):
                  self._make_path(dir_path)
          else:
              dir_path = path.abspath(dir_path)
              if not os.path.exists(dir_path) or not os.path.isdir(dir_path):
                  raise exceptions.ConfigurationException(self.__class__.__name__,
                                                          config.DIRECTORY)
          return dir_path.rstrip('/')
docs: Setup the storage directory path value and ensure the path exists.
  
          :rtype: str
          :raises: tinman.exceptions.ConfigurationException