How to use the kfp.dsl.VolumeSnapshotOp function in kfp

step2_snap = dsl.VolumeSnapshotOp(
        name="step2_snap",
        resource_name="step2_snap",
        volume=step2.pvolume
    )

    step3 = dsl.ContainerOp(
        name="step3_copy",
        image="library/bash:4.4.23",
        command=["sh", "-c"],
        arguments=["mkdir /data/step3 && "
                   "cp -av /data/step2/file1 /data/step3/file3"],
        pvolumes={"/data": step2.pvolume}
    )

    step3_snap = dsl.VolumeSnapshotOp(
        name="step3_snap",
        resource_name="step3_snap",
        volume=step3.pvolume
    )

    step4 = dsl.ContainerOp(
        name="step4_output",
        image="library/bash:4.4.23",
        command=["cat", "/data/step2/file1", "/data/step3/file3"],
        pvolumes={"/data": step3.pvolume}
    )

name="create_volume_1",
        resource_name="vol1",
        size="1Gi",
        annotations={"rok/origin": rok_url},
        modes=dsl.VOLUME_MODE_RWM
    )

    step1 = dsl.ContainerOp(
        name="step1_concat",
        image="library/bash:4.4.23",
        command=["sh", "-c"],
        arguments=["cat /data/file*| gzip -c >/data/full.gz"],
        pvolumes={"/data": vop1.volume}
    )

    step1_snap = dsl.VolumeSnapshotOp(
        name="create_snapshot_1",
        resource_name="snap1",
        volume=step1.pvolume
    )

    vop2 = dsl.VolumeOp(
        name="create_volume_2",
        resource_name="vol2",
        data_source=step1_snap.snapshot,
        size=step1_snap.outputs["size"]
    )

    step2 = dsl.ContainerOp(
        name="step2_gunzip",
        image="library/bash:4.4.23",
        command=["gunzip", "-k", "/data/full.gz"],

name="create_volume",
        resource_name="vol1",
        size="1Gi",
        modes=dsl.VOLUME_MODE_RWM
    )

    step1 = dsl.ContainerOp(
        name="step1_ingest",
        image="google/cloud-sdk:272.0.0",
        command=["sh", "-c"],
        arguments=["mkdir /data/step1 && "
                   "gsutil cat %s | gzip -c >/data/step1/file1.gz" % url],
        pvolumes={"/data": vop.volume}
    )

    step1_snap = dsl.VolumeSnapshotOp(
        name="step1_snap",
        resource_name="step1_snap",
        volume=step1.pvolume
    )

    step2 = dsl.ContainerOp(
        name="step2_gunzip",
        image="library/bash:4.4.23",
        command=["sh", "-c"],
        arguments=["mkdir /data/step2 && "
                   "gunzip /data/step1/file1.gz -c >/data/step2/file1"],
        pvolumes={"/data": step1.pvolume}
    )

    step2_snap = dsl.VolumeSnapshotOp(
        name="step2_snap",

vop2 = dsl.VolumeOp(
        name="create_volume_2",
        resource_name="vol2",
        data_source=step1_snap.snapshot,
        size=step1_snap.outputs["size"]
    )

    step2 = dsl.ContainerOp(
        name="step2_gunzip",
        image="library/bash:4.4.23",
        command=["gunzip", "-k", "/data/full.gz"],
        pvolumes={"/data": vop2.volume}
    )

    step2_snap = dsl.VolumeSnapshotOp(
        name="create_snapshot_2",
        resource_name="snap2",
        volume=step2.pvolume
    )

    vop3 = dsl.VolumeOp(
        name="create_volume_3",
        resource_name="vol3",
        data_source=step2_snap.snapshot,
        size=step2_snap.outputs["size"]
    )

    step3 = dsl.ContainerOp(
        name="step3_output",
        image="library/bash:4.4.23",
        command=["cat", "/data/full"],

step1_snap = dsl.VolumeSnapshotOp(
        name="step1_snap",
        resource_name="step1_snap",
        volume=step1.pvolume
    )

    step2 = dsl.ContainerOp(
        name="step2_gunzip",
        image="library/bash:4.4.23",
        command=["sh", "-c"],
        arguments=["mkdir /data/step2 && "
                   "gunzip /data/step1/file1.gz -c >/data/step2/file1"],
        pvolumes={"/data": step1.pvolume}
    )

    step2_snap = dsl.VolumeSnapshotOp(
        name="step2_snap",
        resource_name="step2_snap",
        volume=step2.pvolume
    )

    step3 = dsl.ContainerOp(
        name="step3_copy",
        image="library/bash:4.4.23",
        command=["sh", "-c"],
        arguments=["mkdir /data/step3 && "
                   "cp -av /data/step2/file1 /data/step3/file3"],
        pvolumes={"/data": step2.pvolume}
    )

    step3_snap = dsl.VolumeSnapshotOp(
        name="step3_snap",