func_code: def swap_unique_keys_values(d):
      dic1 = {}
      dic2 = {}
      dicsort = sorted(list(d.items()), reverse=True)
      for k, v in dicsort:
          if v not in dic1:
              dic1[v] = k
          else:
              dic1[v] = 'N'
      dicsort2 = sorted(list(dic1.items()), reverse=True)
      for k, v in dicsort2:
          if v != 'N':
              dic2[k] = v
      return dic2