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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 get_network_mode(value):
 """ Generates input for the ``network_mode`` of a Docker host configuration. If it points at a container, the configuration of the container is returned. :param value: Network mode input. :type value: unicode | str | tuple | list | NoneType :return: Network mode or container to re-use the network stack of. :rtype: unicode | str | tuple | NoneType """

    if not value or value == 'disabled':
        return 'none'
    if isinstance(value, (tuple, list)):
        if len(value) == 2:
            return tuple(value)
        return ValueError("Tuples or lists need to have length 2 for container network references.")
    if value in DEFAULT_PRESET_NETWORKS:
        return value
    if value.startswith('container:'):
        return value
    if value.startswith('/'):
        return 'container:{0}'.format(value[1:])
    ref_name, __, ref_instance = value.partition('.')
    return ref_name, ref_instance or None