An function to load an object with a specific version of the class.

        Parameters
        ----------
        pickler : file
            A GLUnpickler file handle.

        version : int
            A version number as maintained by the class writer.

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

        Parameters
        ----------
        pickler : file
            A GLUnpickler file handle.

        version : int
            A version number as maintained by the class writer.
        """
        obj = unpickler.load()
        return TransformerChain(obj._state["steps"])