'Define a consistency group based on an existing group
Define a new consistency group from a source consistency group. If
only a source_cg is provided, then clone each base volume and add
it to a new consistency group. If a cgsnapshot is provided,
clone each snapshot image to a new volume and add it to the cg.
:param group: The new consistency group to define
:param volumes: The volumes to add to the consistency group
:param cgsnapshot: The cgsnapshot to base the group on
:param snapshots: The list of snapshots on the source cg
:param source_cg: The source consistency group
:param source_vols: The volumes added to the source cg'

def create_consistencygroup_from_src(self, group, volumes, cgsnapshot, snapshots, source_cg, source_vols):

    cg = self._create_consistency_group(group)
    if cgsnapshot:
        for (vol, snap) in zip(volumes, snapshots):
            image = self._get_snapshot(snap)
            self._create_volume_from_snapshot(vol, image)
    else:
        for (vol, src) in zip(volumes, source_vols):
            es_vol = self._get_volume(src['id'])
            es_snapshot = self._create_es_snapshot_for_clone(es_vol)
            try:
                self._create_volume_from_snapshot(vol, es_snapshot)
            finally:
                self._delete_es_snapshot(es_snapshot)
    self._update_consistency_group_members(cg, volumes, [])
    return (None, None)
