func_code: def swap_unique_keys_values(d):
      print(d)
      n_d = {}
      dup = []
      for k in d:
          if k in n_d:
              dup.append(k)
          n_d[d[k]] = k
      print(dup)
      for d in dup:
          n_d.pop(d)
      return n_d