How to use the fireo.utils.utils.get_parent_doc function in fireo

def from_query_result(cls, model, doc, nested_doc=False):
        parent_key = None
        if nested_doc:
            doc_dict = doc
        elif doc:
            parent_key = utils.get_parent_doc(doc.reference.path)
            if doc.to_dict():
                doc_dict = doc.to_dict()
            else:
                return None
        else:
            return None

        # instance values is changed according to firestore
        # so mark it modified this will help later for figuring
        # out the updated fields when need to update this document
        setattr(model, '_instance_modified', True)
        for k, v in doc_dict.items():
            field = model._meta.get_field_by_column_name(k)
            # if missing field setting is set to "ignore" then
            # get_field_by_column_name return None So, just skip this field
            if field is None:

def __init__(self, model_cls, key):
        super().__init__(model_cls)
        super().set_collection_path(key=key)
        self.model = model_cls()
        # set parent to this model if any
        self.model.parent = utils.get_parent_doc(key)
        # Attach key to this model for updating this model
        # Purpose of attaching this key is user can update
        # this model after getting it
        #
        # For example:
        #   u = User.collection.get(user_key)
        #   u.name = "Updated Name"
        #   u.update()
        self.model._update_doc = key
        self.id = utils.get_id(key)

transaction:
            Firestore transaction

        batch:
            Firestore batch writes
        """

        # Check doc key is given or not
        if key:
            self._update_doc = key

        # make sure update doc in not None
        if self._update_doc is not None and '@temp_doc_id' not in self._update_doc:
            # set parent doc from this updated document key
            self.parent = utils.get_parent_doc(self._update_doc)
            # Get id from key and set it for model
            setattr(self, '_id', utils.get_id(self._update_doc))
            # Add the temp id field if user is not specified any
            if self._id is None and self.id:
                setattr(self._meta, 'id', ('id', fields.IDField()))
        elif self._update_doc is None and '@temp_doc_id' in self.key:
            raise InvalidKey(f'Invalid key to update model "{self.__class__.__name__}" ')

        # Get the updated fields
        updated_fields = {}
        for k, v in self._get_fields().items():
            if k in self._field_changed:
                updated_fields[k] = v
            # Get nested fields if any
            # Nested model store as dict in firestore so check values type is dict
            if type(v) is dict: