Get key from the :attr:`zeo` database root. If the key doesn't exist,
        create it by calling `new_type` argument.

        Args:
            key (str): Key in the root dict.
            new_type (func/obj): Object/function returning the new instance.

        Returns:
            obj: Stored object, or `new_type`.

def _zeo_key(self, key, new_type=OOBTree):
        """
        Get key from the :attr:`zeo` database root. If the key doesn't exist,
        create it by calling `new_type` argument.

        Args:
            key (str): Key in the root dict.
            new_type (func/obj): Object/function returning the new instance.

        Returns:
            obj: Stored object, or `new_type`.
        """
        zeo_key = self.zeo.get(key, None)

        if zeo_key is None:
            zeo_key = new_type()
            self.zeo[key] = zeo_key

        return zeo_key