serializable.py

import inspect
import json
from typing import Dict, TypeVar


SerializableADT = TypeVar("SerializableADT", bound="Serializable")


class Serializable:

    @classmethod
    def from_json(cls, content: str) -> SerializableADT:
        serializable_kwargs = json.loads(content)
        return cls.__init__(**serializable_kwargs)

    def to_dict(self) -> Dict:
        args = inspect.getfullargspec(self.__init__).args
        dictionary = self.__dict__
        return {
            arg: dictionary.get(arg)
            for arg in args
            if arg != "self"
        }

    def to_json(self, **kwargs) -> str:
        dictionary = self.to_dict()
        return json.dumps(dictionary, **kwargs)

serializable_example.py

from serializable import Serializable


class A(Serializable):
    
    def __init__(self, a: str, value: str):
        self.a = a
        self.value = value
        
class B(Serializable):
    
    def __init__(self, b: int):
        self.b = b
        
    def add(val: int) -> 'B':
        return B(self.b + val)


a = A("hello", "world")
a.to_dict()
a.to_json()