How to save model object using only foreign keys id in django-rest-framework

If you want save some data like me in a model which has foreign key field and want to save only by id in foreign key field. Then this method is for you 🐎

models.py
Here is the foreign key field where I want to save this object just passing foreign key id.

In serializers.py we have to put serializers.PrimaryKeyRelatedField on foreign key field name like this -

unit = serializers.PrimaryKeyRelatedField(queryset= Unit.objects.all(),many=False)