docs: def copy_resource(self, container, resource, local_filename):
          """
          *Experimental:* Copies a resource from a Docker container to a local tar file. For details, see
          :meth:`docker.client.Client.copy`.
  
          :param container: Container name or id.
          :type container: unicode | str
          :param resource: Resource inside the container.
          :type resource: unicode | str
          :param local_filename: Local file to store resource into. Will be overwritten if present.
          :type local_filename: unicode | str
          """
          raw = self.copy(container, resource)
          with open(local_filename, 'wb+') as f:
              for buf in raw:
                  f.write(buf)