Replace `assert()` calls with `if`/`else`/`raise <Exception>()`

[hugodahl]

Per a conversation in the FXAS21002C library on issue #21, checking for conditions and raising an exception is preferable over calling assert(). This is preferable for a number of reasons, including memory usage.

[syedmalimustafa]

Can I take this?

[jposada202020]

@alimustafashah Thanks for your interest, for sure thank you very much, that would be really appreciated. thanks :)

[syedmalimustafa]

Can you assign the task to me?

[jposada202020]

@alimustafashah if this is your first time contributing to CP
Teh following information could be helpful
code is reviewed by the CI so ths learning guide is very useful https://learn.adafruit.com/improve-your-code-with-pylint
If will facilitate things if you use pre-commit:
pre-commit run --all-files
And in case you change any documentation, in the docs directory built the documentation locally
sphinx-build -E -W -b html . _build/html

Thanks :)

[syedmalimustafa]

Thanks for sharing!

[jposada202020]

Solved by #30