code: def prune_builds(self):
          
          url = self._url("/build/prune")
          return self._result(self._post(url), True)
docs: Delete the builder cache
  
          Returns:
              (dict): A dictionary containing information about the operation's
                      result. The ``SpaceReclaimed`` key indicates the amount of
                      bytes of disk space reclaimed.
  
          Raises:
              :py:class:`docker.errors.APIError`
                  If the server returns an error.