code: def convert_missing_indexer(indexer):
      
  
      if isinstance(indexer, dict):
  
          # a missing key (but not a tuple indexer)
          indexer = indexer['key']
  
          if isinstance(indexer, bool):
              raise KeyError("cannot use a single bool to index into setitem")
          return indexer, True
  
      return indexer, False
docs: reverse convert a missing indexer, which is a dict
      return the scalar indexer and a boolean indicating if we converted