I have two classes, one is designed to contain the other
class Thing:
    def __init__(self, parent: Box):
        self.parent = parent
        parent.add_to_box(self)
class Box:
    def __init__(self):
        self.children = []
    def add_to_box(self, item: Thing):
        self.children.append(item)
However I can't reference the class types (parent: Box and item: Thing) within each other, only either one or the other.
How can I reference both class types within each other? And otherwise what is the best way to do this?
 
     
    