AttributeError NoneType object has no attribute _inbound_nodes

This error occurs when you try to access an attribute or method of a None object, which is not allowed because None has no attributes or methods. In this specific case, it seems that you are trying to access the _inbound_nodes attribute of a None object.

To solve this error, you should check if the object you are trying to access is not None before accessing its attributes or methods. You can use an if statement or a try-except block to handle this case.