code: def reindex_axis(self, new_index, axis, method=None, limit=None,
                       fill_value=None, copy=True):
          
          new_index = ensure_index(new_index)
          new_index, indexer = self.axes[axis].reindex(new_index, method=method,
                                                       limit=limit)
  
          return self.reindex_indexer(new_index, indexer, axis=axis,
                                      fill_value=fill_value, copy=copy)
docs: Conform block manager to new index.