Creating nested serializers

If we want to include more information about each module, we need to serialize Module objects and nest them. Modify the previous code of the api/serializers.py file of the courses application to make it look as follows:

from django.db.models import Count
from rest_framework import serializers
from courses.models import Course, Module, Subject
class ModuleSerializer(serializers.ModelSerializer):
    class Meta:
        model = Module
        fields = ['order', 'title', 'description']
class CourseSerializer(serializers.ModelSerializer):
    modules = ModuleSerializer(many=True, read_only=True)
    class Meta:
        # ...

In the new code, you define ModuleSerializer to provide serialization for the Module model. Then, you modify the modules attribute of CourseSerializer to nest the ModuleSerializer serializer. You keep many=True to indicate that you are serializing multiple objects and read_only=True to keep this field...