Forbids classes with too high coupling

Rule request

Thesis

Coupling is a very important concept in programming.

Currently, we don't enforce any rules about cohesion and coupling. But, we totally need to!

And while you can use https://github.com/mschwager/cohesion to measure cohesion, there's no tool to measure coupling.

I don't think that cohesion is important. Because the best class in my opinion is @dataclass:

@dataclass
def Some(object):
    field1: int
    field2: str

But, coupling is the whole other beast! High coupling makes refactoring very hard. Compare these two samples:

class SomeClass(ParentClass):
     def method(self, other):
          if other.some_field > other.other_field:
               other.first_method()
          else:
               other.other_method()

And:

class SomeClass(ParentClass):
     def method(self, other):
         other.smart_method()

The second one is way better.

Problems:

1. I am not sure how to count coupling
2. I am not sure about corner values

The issue names no files, tests, or entry points. Start by deciding how coupling should be counted and what corner values mean, then locate the existing rule structure and add tests for the agreed thresholds. Done means a documented, deterministic coupling rule with tests.