code: def new_keypair(key, value, ambig, unambig):
      
      if key in ambig:
          return
  
      if key in unambig and value != unambig[key]:
              ambig.add(key)
              del unambig[key]
              return
  
      unambig[key] = value
      return
docs: Check new keypair against existing unambiguous dict
  
      :param key: of pair
      :param value: of pair
      :param ambig: set of keys with ambig decoding
      :param unambig: set of keys with unambig decoding
      :return: