code: def _read_mode_rsralt(self, size, kind):
          
          if size != 4:
              raise ProtocolError(f'{self.alias}: [Optno {kind}] invalid format')
  
          _code = self._read_unpack(2)
  
          data = dict(
              kind=kind,
              type=self._read_opt_type(kind),
              length=size,
              alert=_ROUTER_ALERT.get(_code, 'Reserved'),
              code=_code,
          )
  
          return data
docs: Read Router Alert option.
  
          Positional arguments:
              size - int, length of option
              kind - int, 148 (RTRALT)
  
          Returns:
              * dict -- extracted Router Alert (RTRALT) option
  
          Structure of Router Alert (RTRALT) option [RFC 2113]:
              +--------+--------+--------+--------+
              |10010100|00000100|  2 octet value  |
              +--------+--------+--------+--------+
  
              Octets      Bits        Name                    Description
                0           0     ip.rsralt.kind          Kind (148)
                0           0     ip.rsralt.type.copy     Copied Flag (1)
                0           1     ip.rsralt.type.class    Option Class (0)
                0           3     ip.rsralt.type.number   Option Number (20)
                1           8     ip.rsralt.length        Length (4)
                2          16     ip.rsralt.alert         Alert
                2          16     ip.rsralt.code          Alert Code