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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def add_unit_to_channel(current):
 """ Subscribe users of a given unit to given channel JSON API: .. code-block:: python # request: { 'view':'_zops_add_unit_to_channel', 'unit_key': key, 'channel_key': key, 'read_only': boolean, # true if this is a Broadcast channel, # false if it's a normal chat room } # response: { 'existing': [key,], # existing members 'newly_added': [key,], # newly added members 'status': 'Created', 'code': 201 } """

    read_only = current.input['read_only']
    newly_added, existing = [], []
    for member_key in UnitModel.get_user_keys(current, current.input['unit_key']):
        sb, new = Subscriber(current).objects.get_or_create(user_id=member_key,
                                                            read_only=read_only,
                                                            channel_id=current.input['channel_key'])
        if new:
            newly_added.append(member_key)
        else:
            existing.append(member_key)

    current.output = {
        'existing': existing,
        'newly_added': newly_added,
        'status': 'OK',
        'code': 201
    }