That will allow the CI workflow to continue

That hopefully prevents the error "codecov failed with exit code 255".

This condition has been checked at the beginning of the function.

Noticed this in the code coverage report.

It's not really about security

Use 'elif' instead of 'if' to avoid wrong self.result when
self.state is 'off'.

We need unit-tests for the engine checking the correctness: #79

These objects should be compared for identity with None using 'is' operator.

Part IV, sys.exit()

Part III, strings

Part II, assert()

Part I, print()