Add _contains_html function

[michael-bentz]

What does this change do?

Adds _contains_html function with unit tests.

Why was this change made?

To close #3.

Verification

1. Verify the logic of the test_contains_html unit test
2. Verify that all automated workflows pass

• Verify the thing does this: ...
• Verify the thing does not do that: ...

Affirmations

All of these should have a check by them. Any exception requires an explanation.

• I have added docstrings with details on keyword arguments to new functions following the convention detailed in this gist
• I have added type hinting to new function parameters.
• I have added tests to new functions, following the rules of F.I.R.S.T..
• I matched the style of the existing code.
• I added and updated any relevant documentation (inline, README, CHANGELOG, and such).
• I used Python's type hinting.
• I ran the automated tests and ensured they ALL passed.
• I ran the linter and ensured my changes have not introduced ANY warnings or errors.
• I have made an effort to minimize code changes and have not included any cruft (preference files, *.pyc files, old comments, print-debugging, unused variables).
• I have made an effort maintain a clear commit history (haven't merged other branches or rebased improperly).
• I have written the code myself or have given credit where credit is due.

[mehuljhaver4]

• Verified the logic of the test_contains_html unit test
• Verified that all automated workflows passed

[mehuljhaver4]

line 16 and similar lines show the following problem:

Cannot access member "assertEquals" for type "TestUtils" Member "assertEquals" is unknownPylanc reportGeneralTypeIssues

But the tests run successfully

[michael-bentz]

I'm not sure how you're getting this. I don't see it locally and the lint workflow is passing.

[mehuljhaver4]

Must be some issue at my end. I'll merge it.