def _mapper_arg_chain(self, step_dict, step_num, input_path):
        # sometimes the mapper isn't actually there, so if it isn't, use cat
        if 'mapper' not in step_dict:
            new_step_dict = {
                'mapper': {
                    'type': 'command',
                    'command': 'cat',
                }
            }
            new_step_dict.update(step_dict)
            step_dict = new_step_dict

        procs_args = self._substep_arg_chain(
            'mapper', step_dict, step_num, input_path)

        if step_dict in 'combiner':
            procs_args.append(['sort'])
            # _substep_args may return more than one process
            procs_args.extend(self._combiner_arg_chain(step_dict, step_num))

        return procs_args
dataset/ETHPy150Open Yelp/mrjob/mrjob/local.py/LocalMRJobRunner._mapper_arg_chain/swapped operands of `in`