this works for me in the IDE but the challenge keeps telling me it can't get length

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):
        super().__init__(sides=20)

class Hand(list):

    def clear_hand(self):
        del self[:]

    def total(self):
        return sum(self)

    def roll(self, amt_dice):
        x = 1
        while x <= amt_dice:
            foo = D20()
            self.append(int(foo))
            x = x + 1