Signing Apple secret key

I have followed the steps in this tutorial: https://learn.microsoft.com/en-us/azure/active-directory-b2c/identity-provider-apple-id?pivots=b2c-custom-policy to create an Apple sign in for my application. From the Apple Developer Portal menu, I went to Certificates, IDs, & Profiles and created a Key. I then tried to sign the key be using this python script:

import jwt
import time

def generate_token():
    private_key = """[pasted key from Apple here]"""  
    team_id = "[pasted team_id]"
    client_id = "[pasted client_id]"
    key_id = "[pasted key_id]"
    validity_minutes = 20
    timestamp_now = int(time.time())
    timestamp_exp = timestamp_now + (60 * validity_minutes)
    data = {
        "iss": team_id,
        "iat": timestamp_now,
        "exp": timestamp_exp,
        "aud": "https://appleid.apple.com",
        "sub": client_id
    }
    token = jwt.encode(
        payload=data,
        key=private_key,  # Use the key directly without encoding as 'utf-8', jwt.encode handles this.
        algorithm="ES256",
        headers={"kid": key_id}
    )
    print(token)

generate_token()

I don't think this worked because I am getting an error after I sign in. Is there some other script I can use?