What should be the messageType for a custom message?

edit

HI,

I created a custom ROS message:

string message
int32 a
int32 b

I will need to publish the messages from the web browser (roslibjs) and show it on the terminal, using python. Roslibjs requires us to specify a messageType when we start a topic, for example:

var msgTopic = new ROSLIB.Topic({
ros: ros,
name: 'chatter',
messageType: <messageType??>
});

I don't know what would be the messageType here, for my custom message. I would appreciate any help with this. Thank you!