Django Rest Framework nested serializer gives attribute error - django

Question

I am trying to setup a nested serializer below I've posted the models and serializer. why am I getting the below error ?
Got AttributeError when attempting to get a value for field `balance_sheet` on serializer `StockSerializer`.
The serializer field might be named incorrectly and not match any attribute or key on the `Stock` instance.
Original exception text was: 'Stock' object has no attribute 'balance_sheet'.
serializers.py
class StockSerializer(serializers.ModelSerializer):
income_statement = IncomeStatementSerializer(many=True)
balance_sheet = BalanceSheetSerializer(many=True)
cashflows_statement = CashflowsStatementSerializer(many=True)
def create(self, validated_data):
temp_income_statement_data = validated_data.pop("income_statement")
temp_balance_sheet_data = validated_data.pop("balance_sheet")
temp_cashflows_statement_data = validated_data.pop("cashflows_statement")
new_stock = Stock.objects.create(**validated_data)
for i in temp_income_statement_data:
IncomeStatement.objects.create(**i, ticker=new_stock)
for x in temp_balance_sheet_data:
BalanceSheet.objects.create(**x, ticker=new_stock)
for y in temp_cashflows_statement_data:
CashflowsStatement.objects.create(**y, ticker=new_stock)
return new_stock
IncomeStatementSerializer, BalanceSheetSerializer and CashflowsStatementSerializer are all typical ModelSerializer's
models.py
class Stock(models.Model):
id = models.UUIDField(default=uuid.uuid4, editable=False, unique=True)
ticker = models.CharField(max_length=10, unique=True, primary_key=True)
slug = models.SlugField(default="", editable=False)
def save(self, *args, **kwargs):
value = self.ticker
self.slug = slugify(value, allow_unicode=True)
super().save(*args, **kwargs)
def __str__(self):
return self.ticker
class Meta:
verbose_name = "stock"
verbose_name_plural = "stocks"
ordering = ["ticker"]
IncomeStatement, BalanceSheet and CashflowsStatement are all typical models.Model with a ForeignKey relationship to Stock
views.py
class StockList(generics.ListCreateAPIView):
queryset = Stock.objects.all()
serializer_class = StockSerializer
lookup_field = "slug"