tkinter: Fix return type of winfo_children()

[Akuli]

The winfo_children() method returns a list of the child widgets of a widget. Previously I thought this could never be Toplevel widgets, but that is wrong: they can in fact be anything except tkinter.Tk.

>>> from tkinter import Tk, Toplevel, Button
>>> root = Tk()
>>> top = Toplevel()
>>> button = Button()
>>> root.winfo_children()
[<tkinter.Toplevel object .!toplevel>, <tkinter.Button object .!button>]
>>> 

Tk can never be the child of another widget, because it is a special widget and each instance of Tk is internally a whole new Tcl interpreter.

Ideally, the type of this would be Misc & ~Tk; that is, any widget except Tk. But because & and ~ operators on types don't exist yet, the best we can do is Widget | Toplevel. Misleadingly, Widget in tkinter means any widget except Tk or Toplevel, and Misc means any widget.

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉

[Avasam]

Your explanation makes sense to me.