* Fix a statement about coupling and cohesion that is not always true
https://enterprisecraftsmanship.com/posts/cohesion-coupling-difference/#_types_of_code_from_a_cohesion_and_coupling_perspective
* Fix a typing issue in an example
`ApiClient` expects timeout to be an integer (based on a type hint), but `os.getenv` returns a string when `TIMEOUT` is set.
* Specify the `None` return type where it is missed
* Fix typing issues in some other places
* Edit a statement about coupling and cohesion
Co-authored-by: Roman Mogylatov <rmogilatov@gmail.com>
Co-authored-by: Roman Mogylatov <rmogilatov@gmail.com>
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