docs: def MI_get_item(self, key, index=0):
      'return list of item'
      index = _key_to_index_single(force_list(self.indices.keys()), index)
      if index != 0:
          key = self.indices[index][key]  # always use first index key
      # key must exist
      value = super(MIMapping, self).__getitem__(key)
      N = len(self.indices)
      if N == 1:
          return [key]
  
      if N == 2:
          value = [value]
      return [key] + value