How to make a list of classes serializable? Flask

Question

I have a model of a Message that looks like this

class Message(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    text = db.Column(db.String(300))
    username = db.Column(db.String(150))
    chat_id = db.Column(db.Integer, db.ForeignKey("chat.id"))

And a Chat one that looks like this

class Chat(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    user1 = db.Column(db.String(150), unique=True)
    user2 = db.Column(db.String(150), unique=True)
    room = db.Column(db.String(300), unique=True)
    messages = db.relationship("Message", backref="chat")

I have a socketHandler file which is trying to send information to my home.html page. In that file I have these lines:

messages = Chat.query.filter_by(room=room).first().messages
socketio.emit("room-joined", (room, messages))

However I get an error everytime this runs which says:
TypeError: Object of type Message is not JSON serializable

How do I make it serializable?
Thanks!