what am I doing wrong?

import random


class Die:
    def __init__(self, sides=2):
        if sides < 2:
            raise ValueError("Can't have fewer than two sides")
        self.sides = sides
        self.value = random.randint(1, sides)

    def __int__(self):
        return self.value

    def __add__(self, other):
        return int(self) + other

    def __radd__(self, other):
        return self + other

    class D20(Die):
    def __init__(self,sides=0):
        super().__init__(sides=20)

from dice import D20

class Hand(list):

    def __init__(self, sides=0, die_class =D20):
        super().__init__()
        for _ in range(sides):
            self.append(die_class())

    @classmethod
    def roll(cls, sides=0):
        return cls(sides)

    @property
    def total(self):
        return sum(self)

h = Hand.roll(2) 
h.total