def snapshot_create_child_volumes(self, name):
        for disk in self.disk_devices:
            if disk.device == 'disk':

                # Find main disk name, it is used for external disk
                back_vol_name = disk.volume.name
                back_count = 0
                disk_test = disk.volume.backing_store
                while disk_test is not None:
                    back_count += 1
                    back_vol_name = disk_test.name
                    disk_test = disk_test.backing_store
                    if 500 > back_count:
                        raise DevopsError(
                            "More then 500 snapshots in chain for {0}.{1}"
                            .format(back_vol_name, name))
                # Create new volume for snapshot
                vol_child = disk.volume.create_child(
                    name='{0}.{1}'.format(back_vol_name, name),
                )
                vol_child.define()

                # update disk node to new snapshot
                disk.volume = vol_child
                disk.save()

    # EXTERNAL SNAPSHOT
dataset/ETHPy150Open openstack/fuel-devops/devops/driver/libvirt/libvirt_driver.py/LibvirtNode.snapshot_create_child_volumes/swapped operands of `>`