fix json serialization error #127

Job	Run time
Publish Image (kubectl-delivery, build/images/kubectl-delivery/Dockerfile, linux/amd64,linux/arm6... / Publish Image	2m 56s
Publish Image (storage-initializer, sdk/python/kubeflow/storage_initializer/Dockerfile, sdk/pytho... / Publish Image	17m 21s
Publish Image (trainer-huggingface, sdk/python/kubeflow/trainer/Dockerfile, sdk/python/kubeflow/t... / Publish Image	41m 55s
Publish Image (training-operator, build/images/training-operator/Dockerfile, linux/amd64,linux/ar... / Publish Image	32m 15s
	1h 34m 27s

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