I am working with a DRF serializer which includes a field with the PrimaryKeyRealtedField.

import stripe
from rest_framework import serializers
from subscriptions.models.subscription_product import SubscriptionProduct

class SubscriptionCheckoutSessionSerializer(serializers.Serializer):
   url = serializers.CharField(read_only=True)
   success_url = serializers.CharField(write_only=True, required=False)
   cancel_url = serializers.CharField(write_only=True, required=False)
   subscription_product = serializers.PrimaryKeyRelatedField(
    queryset=SubscriptionProduct.objects.all()
   )

def create(self, validated_data):
    print(validated_data)
    subscription_product = validated_data["subscription_product"]
    print(subscription_product)
    stripe_price = subscription_product.stripe_price
    print(stripe_price)
    print(stripe_price.stripe_id)
    session = stripe.checkout.Session.create(
        success_url=validated_data.get("success_url", None),
        cancel_url=validated_data.get("cancel_url", None),
        mode="subscription",
        line_items=[
            {
                "price": stripe_price.stripe_id,
                "quantity": 1,
            }
        ],
    )
    print(session)
    return session

The print statements all print their expected output and the created session is a valid one. However, I get a 500 status code with the following error:
KeyError: “Got KeyError when attempting to get a value for field subscription_product on serializer SubscriptionCheckoutSessionSerializer.nThe serializer field might be named incorrectly and not match any attribute or key on the Session instance.nOriginal exception text was: ‘subscription_product’.”

Does anyone know what this error actually means and how to solve it? I don’t understand how it’s possible that the print statements work as expected but I still get a key error.