docs: def df(self):
          """
          Get data usage information.
  
          Returns:
              (dict): A dictionary representing different resource categories
              and their respective data usage.
  
          Raises:
              :py:class:`docker.errors.APIError`
                  If the server returns an error.
          """
          url = self._url('/system/df')
          return self._result(self._get(url), True)