Loads a previously serialised pipeline.

def load(cls, serialised):
        """Loads a previously serialised pipeline."""
        pipeline = cls()
        for fn_name in serialised:
            try:
                fn = cls.registered_functions[fn_name]
            except KeyError:
                raise BaseLunrException(
                    "Cannot load unregistered function ".format(fn_name)
                )
            else:
                pipeline.add(fn)

        return pipeline