> If you have a cyclic reference between two files,

Don't have cyclic references between two files.

It makes testing very difficult, because in order to test something in one file, you need to import the other one, even though it has nothing to do with the test.

It makes the code more difficult to read, because you're importing these two files in places where you only need one of them, and it's not immediately clear why you're importing the second one. And it's not very satisfying to learn that you you're importing the second one not because you "need" it but because the circular import forces you to do so.

Every single time you have cyclic references, what you really have are two pieces of code that rely on a third piece of code, so take that third piece, separate it out, and have the first two pieces of code depend on the third piece.

Now things can be tested, imports can be made sanely, and life is much better.