Here is a simple solution for a simple feature:

.toJSON() Method

Instead of a JSON serializable class, implement a serializer method:

import json

class Object:
    def toJSON(self):
        return json.dumps(self, default=lambda o: o.__dict__, 
            sort_keys=True, indent=4)

So you just call it to serialize:

me = Object()
me.name = "Onur"
me.age = 35
me.dog = Object()
me.dog.name = "Apollo"

print(me.toJSON())

will output:

{
    "age": 35,
    "dog": {
        "name": "Apollo"
    },
    "name": "Onur"
}