InMemoryBackingStore infinite loop

Describe the bug

The InMemoryBackingStore class is experiencing an infinite loop when setting values. This occurs because the set method subscribes a lambda function that calls set again, which in turn triggers the subscription callback, causing set to be called repeatedly.

        if isinstance(value, list):
            # if its a collection, subscribe to the collection's item BackingStores and use
            # the events to flag the collection property is "dirty"
            for item in value:
                if isinstance(item, BackedModel) and item.backing_store:
                    item.backing_store.is_initialization_completed = True
                    item.backing_store.subscribe(
                        lambda prop_key, old_val, new_val: self.set(key, value)
                    )

        self.__store[key] = value_to_add
        for sub in list(self.__subscriptions):
            self.__subscriptions[sub](key, old_value, value_to_add)

Because you're invoking the subscription which is calling set which is invoking the subscription.

Expected behavior

The set method should store the value and notify subscribers without causing an infinite loop.

How to reproduce

1. Create an instance of InMemoryBackingStore.
2. Set a value that is a BackedModel or a list containing BackedModel instances.
3. The set method subscribes a lambda function that calls set again.
4. The subscription callback is triggered, causing set to be called repeatedly.

SDK Version

No response

Latest version known to work for scenario above?

No response

Known Workarounds

Awful, but until an update, unsubscribing and re-subscribing around problematic code.

subscription_ids = []

# Collect all backing stores and sub ids as to not modify while iterating
for role in app.app_roles:
    if isinstance(role, BackedModel) and role.backing_store:
        for (
            sub_id,
            callback,
        ) in role.backing_store._InMemoryBackingStore__subscriptions.items():
            if callback.__name__ == "<lambda>":
                subscription_ids.append((role.backing_store, sub_id))

# Unsubscribe lambdas...
for backing_store, sub_id in subscription_ids:
    backing_store.unsubscribe(sub_id)

# Problematic code
for role in app.app_roles:
    if role.is_enabled != enable:
        role.is_enabled = enable

# Resubscribe lambdas...
for backing_store, sub_id in subscription_ids:
    backing_store.subscribe(
        lambda prop_key, old_val, new_val: role.backing_store.set(
            prop_key, new_val
        ),
        sub_id,
    )

Debug output

</details>


### Configuration

_No response_

### Other information

_No response_

首先定位 InMemoryBackingStore 类并检查其 set 方法，尤其是为 BackedModel 值和列表添加的订阅。使用一个 BackedModel 或 BackedModel 实例列表重现该问题，并跟踪 subscriber 通知。完成的标准是：设置值会存储该值并通知 subscriber，同时不会递归调用 set 或进入无限循环。