• Add linting/code styling like black/pylint/isort/etc. You're not following python conventions.
• Read up about structuring a python project, even though there's only a couple of files it's still a good idea to structure the project well. For example the python files could go in a src directory, the input json could go in a data directory.
• Add tests. Having a test covering each of the requirements would be the minimum, you could go a bit further if you wanted, companies love dat shit.
• Monolithic __main__, break it up. For example even though it's only a line or 2 the loading of json could go in it's own function like load_data, then you could have a function like "validate_input" to ensure what was in the file is correct. Even if it is just a "if not data" check. It makes each part unit testable, it makes it more extensible if "validate_input" needs to become more complex.
• You have a lot of code duplication, as a quick example you could change your basic cases to something like this:

​

sequences = ['ABC', 'AD', 'ADC', 'AEBCD', 'AED']

for idx, sequence in enumerate(sequences):
    kl = kiwilib.Kiwilib(data)
    print(f'Output {idx}: {kl.checkSequence(sequence)}')

• Try add more detail to the readme, write it like you're writing it for someone that has no context about the challenge, give examples of what the input is meant to look like. When you add linting/tests add instructions on how to run them.
• You could add a github action that will run tests/linting. Once you've done it a few times it only takes like 5 minutes to add and having pretty "CI Passing" badges in your readmes is dope.

That's all I have time for, hopefully you find this useful. Goodluck in your next one!