@staticmethod
def _set_io_fields(step):
    """ Set io keys as step attributes """
    for item in ['inputs', 'outputs', 'output']:
        step[item] = []
        for task in step['_tasks']:
            true_task = task['task'] if 'task' in task else task
            if item in true_task:
                if isinstance(true_task[item], list):
                    step[item].extend(true_task[item])
                else:
                    step[item].append(true_task[item])
    step['outputs'].extend(step['output'])
    step['inputs'] = list(set(step['inputs']))
    for task in step['_tasks']:
        step['chunk'] = True if 'chunk_number' in task else False
