'Infer the Flocker manifestation which is in use by the given container.
:param flocker.node._docker.Unit container: The container to inspect.
:param dict path_to_manifestations: A mapping from mount points (as
``FilePath``) to identifiers (as ``unicode``) of the datasets that
are mounted there.
:return: ``None`` if no Flocker manifestation can be associated with
the container state.  Otherwise an ``AttachedVolume`` referring to
that manifestation and the location in the container where it is
mounted.'

def _attached_volume_for_container(self, container, path_to_manifestations):

    if container.volumes:
        docker_volume = list(container.volumes)[0]
        try:
            manifestation = path_to_manifestations[docker_volume.node_path]
        except KeyError:
            return None
        else:
            return AttachedVolume(manifestation=manifestation, mountpoint=docker_volume.container_path)
    return None
