func_code: def swap_unique_keys_values(dic):
      a, b, c = [], [], {}
      for file in dic:
          if file in a:
              a.pop(a.index(dic[file]))
          else:
              a.append([file, dic[file]])
          print(a)
      for letter in a:
          print(letter)
          if letter[1] in c:
              del c[letter[1]]
          else:
              c[letter[1]] = letter[0]
      print(c)
      return c