func_code: def swap_unique_keys_values(d):
      A = '@@'
      keys = []
      values = []
      dic = {}
      for k, v in list(d.items()):
          keys.append(k)
          values.append(v)
      i = 0
      while i < len(values):
          j = 0
          while j < len(values):
              if values[i] == values[j] and i != j:
                  values[i] == A
                  values[j] == A
              j = j + 1
          i = i + 1
      i = 0
      while i < len(values) and values[i] != A:
          dic[values[i]] = keys[i]
          i = i + 1
      return dic