code: def get_index(self, key: Hashable) -> pd.Index:
          
          if key not in self.dims:
              raise KeyError(key)
  
          try:
              return self.indexes[key]
          except KeyError:
              # need to ensure dtype=int64 in case range is empty on Python 2
              return pd.Index(range(self.sizes[key]), name=key, dtype=np.int64)
docs: Get an index for a dimension, with fall-back to a default RangeIndex