func_code: def swap_unique_keys_values(d):
      counter = {}
      for v in list(d.values()):
          counter[v] = counter.get(v, 0) + 1
      unique = {k: v for k, v in list(d.items()) if counter[v] == 1}
      new_d = {val: key for key, val in list(unique.items())}
      return new_d