@classmethod
def _load_version(cls, state, version):
    """
        An function to load an object with a specific version of the class.

        WARNING: This implementation is very simple.
                 Overwrite for smarter implementations.

        Parameters
        ----------
        state : dict
            The saved state object

        version : int
            A version number as obtained from _get_version()
        """
    raise NotImplementedError('load')
