Python: circular definitions between classes? [duplicate]

I want to create two classes (Spectrogram and TimeWindow) which should recall one another, but I'm not sure about my definitions. I first define Spectrogram and then TimeWindow afterwards. The logic when using the objects is the following:

1. The window = TimeWindow() object is created
2. I have a method which creates a spect = Spectrogram() object, and sets it as attribute of window
3. I set the window object as attribute of the spect object, because I want to be able to get one from the other.

First question

The code seems to work. Is this architecture ok? Is there a cleaner way to achieve the fact that I can access one object from the other?

Second question

I tried to define the Spectrogram class as follows, imposing that the input variable time_window is of type TimeWindow. This results in an error, because I define the TimeWindow class after the Spectrogram class. Is there any way to impose the type of time_window?

class Spectrogram:

    def __init__(self, time_window:TimeWindow, ...):

        self.time_window = time_window
        ...

Thank you everyone!