code: def _level_coords(self):
          
          level_coords = OrderedDict()
          for name, index in self.indexes.items():
              if isinstance(index, pd.MultiIndex):
                  level_names = index.names
                  (dim,) = self.variables[name].dims
                  level_coords.update({lname: dim for lname in level_names})
          return level_coords
docs: Return a mapping of all MultiIndex levels and their corresponding
          coordinate name.