func_code: def swap_unique_keys_values(x):
      sorx = sorted(x.items, reverse=True)
      x1 = {}
      x2 = {}
      for keys, values in sorx:
          if v not in x1:
              x1[values] = keys
          else:
              x1[v] = 'N'
      sorx2 = sorted(list(x1.items()), revers=True)
      for keys, values in sorx2:
          if v != sorx2:
              x2[keys] = values
      return x2