/kind feature

This is a sub-issue from #5494.
We need to remove any f"strings" from the backend of the Jupyter web app in order to be able to use lower versions from Python 3.6 to run it.

/good-first-issue

As suggested in this issue comment, the code snippets documentation needs to be more clear about its metadata properties and better describe them.
![image](https://user-images.githubusercontent.com/25207344/107660274-13328f80-6c56-11eb-95a0-471c291b8ce2.p

Deploy kfserving v0.3.0 and sample app

kubectl apply -f kfserving.v0.3.0.yaml
kubectl apply -f sklearn.yaml

I have k8s cluster with enabled PSP and ImagePullAlways plugin
https://kubernetes.io/docs/reference/access-authn-authz/admission-controllers/
After all kservice isn't working

kubectl describe replicaset.apps/sklearn-iris-predictor-default-x9v87-deployment-784dbd

This could be example that uses these supported syntax and APIs:

https://github.com/couler-proj/couler/tree/d34a690/couler/core/syntax