code: def _level_coords(self):
          
          level_coords = OrderedDict()
          for cname, var in self._coords.items():
              if var.ndim == 1 and isinstance(var, IndexVariable):
                  level_names = var.level_names
                  if level_names is not None:
                      dim, = var.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.