Get rid of import * in the readme and elsewhere

[MrPowers]

import * is a Python antipattern.

Let's get rid of it everywhere.

[paulooctavio]

@MrPowers Can I get this one?

[paulooctavio]

@SemyonSinchenko How should the import * in the README be replaced? I'm running into a TypeError: 'Column' object is not callable when trying to use any of the Column Extensions (e.g. isFalsy, isTruthy, etc.) after importing quinn.

Also, is F referring to from pyspark.sql import functions as F?

[SemyonSinchenko]

@paulooctavio Sorry for a long answer. You need to directly call a function like quinn.functions.is_falsy(col)
P.S. Feel free to ping me if I'm not responding

[MrPowers]

I am looking here: https://github.com/mrpowers-io/quinn/blob/main/quinn/__init__.py#L41

Think we should recommend import quinn and then quinn.is_falsy. Hopefully we can expose the whole public interface (or most of it) in the quinn import.