Python: Improve handling of previous overrides in eval command

[jamesL92]

• The PR has a clear title and a concise summary of the changes (Use the present tense and imperative mood for your descriptions)
• Related issues are linked using Closes #number
• Code is up-to-date with the main branch
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Going to say this addresses #247 for the python SDK instead of sing a Closes ticket, as there is still work to be done on the Go SDK for this issue.

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[jamesL92]

Code here basically mirrors the changes made in #250

[RonConfigu]

Looks good 💯

I will merge it to main but my PR will override some of this code since ConfigSchema has changed.

Thanks @jamesL92