class Item:
    def __init__(self, id, name=""):
        self.id = id

    def __repr__(self):
        return self.name

    def is_container(self):
        return False

    def get_id(self):
        return self.id


class Shelf:
    def __init__(self, id):
        self.id = id
        self.items = {}

    def is_container(self):
        return False

    def get_id(self):
        return self.id

    def store_item(self, item):
        if item.is_container():
            return False
        id = item.get_id()
        self.items[id] = item
        return True

class Inventory:
    pass
