New function validate-invariants

[sarahsonder]

Motivation and Context

To explicitly check that the representation invariants of an object are satisfied.

Your Changes

Description:
Created a new function called validate_invariants which takes in an object obj and checks that the representation invariants of obj are satifised.

Type of change

• New feature (non-breaking change which adds functionality)

Testing

Created testing suite test_validate_invariants.py.

Checklist

• I have performed a self-review of my own code.
• I have verified that the CI tests have passed.
• I have reviewed the test coverage changes reported on Coveralls.
• I have updated the CHANGELOG.md file.

[david-yz-liu]

@sarahsonder you're definitely on the right track here! In addition to writing tests (of course), my main comment is you've correctly found some existing code on which to base you work. But now that you've done so, the best approach is to refactor your code to remove the duplication, so that the common code is used in existing place and in the new function you've added. This might mean defining new helper methods as appropriate.

[coveralls]

Pull Request Test Coverage Report for Build 5663898953

• 20 of 20 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 94.103%

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Totals
Change from base Build 5579502227:	0.02%
Covered Lines:	3064
Relevant Lines:	3256

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💛 - Coveralls

[david-yz-liu]

@sarahsonder good work. I left some inline comments, but also make sure to add this new function to the contract checking documentation page.