docs: 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