Fix kubeflow#3906 - check that ops to be transformed is a containerOp

sdk/python/kfp/onprem.py

@@ -1,14 +1,18 @@
 
 def mount_pvc(pvc_name='pipeline-claim', volume_name='pipeline', volume_mount_path='/mnt/pipeline'):
     """
-        Modifier function to apply to a Container Op to simplify volume, volume mount addition and 
+        Modifier function to apply to a Container Op to simplify volume, volume mount addition and
         enable better reuse of volumes, volume claims across container ops.
         Usage:
             train = train_op(...)
             train.apply(mount_pvc('claim-name', 'pipeline', '/mnt/pipeline'))
     """
     def _mount_pvc(task):
         from kubernetes import client as k8s_client
+        # there can be other ops in a pipeline (e.g. ResourceOp, VolumeOp)
+        # refer to #3906
+        if not hasattr(task, "add_volume") or not hasattr(task, "add_volume_mount"):
+            return task
         local_pvc = k8s_client.V1PersistentVolumeClaimVolumeSource(claim_name=pvc_name)
         return (
             task