code: def access_key(self, data):
          
          if data.startswith(b'h:'):
              new = binascii.unhexlify(data[2:])
          else:
              new = data
          if len(new) == 6:
              self.access_code = new
          else:
              raise yubico_exception.InputError('Access key must be exactly 6 bytes')
docs: Set a new access code which will be required for future re-programmings of your YubiKey.
  
          Supply data as either a raw string, or a hexlified string prefixed by 'h:'.
          The result, after any hex decoding, must be 6 bytes.