Load a workflow
        cls - workflow class (to get __name__ from)
        run_id - id given to the specific run

def load(self, cls, run_id):
        """
        Load a workflow
        cls - workflow class (to get __name__ from)
        run_id - id given to the specific run
        """
        id_code = self.generate_load_identifier(cls, run_id)
        inst = self.store.load(id_code)
        return inst