Django-rest framework 'module' object is not callable

[antat2003]

I have a model like this
class ProductCategory(models.Model):
name = models.CharField(max_length=150, primary_key = True)
description = models.TextField()

audit_log = AuditLog()

my serializer:

class ProductCategorySerializer(serializers.ModelSerializer):
class Meta:
model = ProductCategory

I got this error
TypeError at /api/productcategoty/
'module' object is not callable

Do you know how to implement AuditLog() to work with rest framework?
Thank you
An