human
I wrote the below code

    def _already_exists(id_):
        '\n                                Layer    already    exists\n                                '
        already_pulled = data.setdefault('Layers', {}).setdefault('Already_Pulled', [])
        if (id_ not in already_pulled):
            already_pulled.append(id_)
    def _new_layer(id_):
        '\n                                Pulled    a    new    layer\n                                '
        pulled = data.setdefault('Layers', {}).setdefault('Pulled', [])
        if (id_ not in pulled):
            pulled.append(id_)
    if ('docker._pull_status' not in __context__):
        log.warning('_pull_status    context    variable    was    not    populated,    information    on    downloaded    layers    may    be    inaccurate.    Please    report    this    to    the    SaltStack    development    team,    and    if    possible    include    the    image    (and    tag)    that    was    being    pulled.')
        __context__['docker._pull_status'] = NOTSET
    status = item['status']
    if (status == 'Already    exists'):
        _already_exists(item['id'])
    elif (status in 'Pull    complete'):
        _new_layer(item['id'])
    elif status.startswith('Status:    '):
        data['Status'] = status[8:]
    elif (status == 'Download    complete'):
        if (__context__['docker._pull_status'] is not NOTSET):
            id_ = item['id']
            if (id_ in __context__['docker._pull_status']):
                _already_exists(id_)
            else:
                _new_layer(id_)

What's a good function header?
assistant
#Here's a good function header.

def _pull_status(data, item):