chore: fix incorrect comparison operators

[wimlewis-amazon]

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Description

Changes comparisons to use identity-comparison (is) for the singleton None, and value-comparison (==) for strings.

Why is the change necessary?

Python strings do not guarantee object identity for equal strings, so comparing self.type against a string using is might not have the intended effect. (In practice, since both values are short constant string literals from the same source file, it'll work … but it's bad practice, and generates both runtime warnings and linter warnings.)

Using is not None instead of != None is less important, but it's accepted Python style to use is/is not for the None singleton, and linters throw warnings on this as well.

Solution

How was this change tested?

tox tests/unit has the same number of failures after this change as before.

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Pull Request Checklist

Please check all boxes (including N/A items)

Testing

• [X] Unit tests added (no behavior change)
• [X] Integration test added (not needed)
• [X] Manual testing (not needed)

Documentation

• [X] docs: No relevant docs
• [X] docstrings: No changes to public API

Title and description

• [X] Change type: Title is prefixed with change type: and follows conventional commits
• [X] References: Indicate issues fixed via: Fixes #xxx (no issue created for this PR)

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license.