Fix pyright type error to assert that actions can't be an int.

[yjhan96]

Description

When I ran pre-commit run --all-files locally, there were two pyright errors, and I think the error is valid - numpy doesn't provide enough type context to tell pyright that tolist() will not return a scalar if the instance isn't a scalar. Since np.flatnonzero never returns a scalar, asserting that the return value of tolist() is never an int seems reasonable to fix pyright error.

Fixes #1269 .

Type of change

Bug fix (non-breaking change which fixes an issue)

Checklist:

• I have run the pre-commit checks with pre-commit run --all-files (see CONTRIBUTING.md instructions to set it up)
• I have run pytest -v and no errors are present.
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I solved any possible warnings that pytest -v has generated that are related to my code to the best of my knowledge.
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes