code: def RequestPacket(self):
          
  
          attr = self._PktEncodeAttributes()
  
          if self.id is None:
              self.id = self.CreateID()
  
          header = struct.pack('!BBH', self.code, self.id, (20 + len(attr)))
          self.authenticator = md5_constructor(header[0:4] + 16 * six.b('\x00') + attr
              + self.secret).digest()
          return header + self.authenticator + attr
docs: Create a ready-to-transmit authentication request packet.
          Return a RADIUS packet which can be directly transmitted
          to a RADIUS server.
  
          :return: raw packet
          :rtype:  string