Replace assertions with valueError Exeptions

[jyshdewangan]

What does this PR do?

Fixes # (issue)

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@sgugger Please review

[jyshdewangan]

Contributes toward fixing #12789

[sgugger]

Thanks a lot foe fixing those!

[jyshdewangan]

Hey @sgugger, can you please add hactoberfest-accepted tag also?

[sgugger]

According to the rules, it's not necessary when the PR has been approved and merged:

A pull request is considered approved once it has an overall approving review from maintainers, or has been merged by maintainers, or has been given the 'hacktoberfest-accepted' label.*