func_code: def swap_unique_keys_values(in_dict):
      dict_out = {}
      not_unique = set()
      for k, v in list(in_dict.items()):
          if v in dict_out:
              not_unique.update([v])
              del dict_out[v]
          elif v not in not_unique:
              dict_out[v] = k
      return dict_out