Serializer for child class

I am having following Models in my project:

Site: site = models.CharField(max_length=30, blank=False, null=False)
approver = models.ForeignKey(User, on_delete=models.DO_NOTHING, related_name="design_site_approver",  blank=True, null=True, limit_choices_to={'is_approver': True})
submitter = models.ForeignKey(User, on_delete=models.DO_NOTHING, related_name="design_site_submitter",  blank=True, null=True)

Comment: user = models.ForeignKey(User, on_delete=models.CASCADE, related_name='user_name_comment')
    timestamp = models.DateTimeField(
    remarks = models.TextField(null=True, blank=True)
    parent = models.ForeignKey('self', on_delete=models.CASCADE, null=True, blank=True, related_name='replies')
    site = models.ForeignKey(InDesignSite, on_delete=models.CASCADE, related_name='site_name_comment')

File: site = models.ForeignKey(InDesignSite, on_delete=models.CASCADE, related_name='site_name')
    def upload_to_path(self, filename):
        site =
        return f'/{site}/{filename}'
    attachment = models.FileField(upload_to=upload_to_path)

Following is my serializer file:

Comment: class CommentSerializer(serializers.ModelSerializer):
class Meta:
    model = Comment
    fields = '__all__'

Files: class FileSerializer(serializers.ModelSerializer):
class Meta:
    model = Files
    fields = '__all__'

Site: class SiteSerializer(serializers.ModelSerializer):
      remarks = CommentSerializer(many=True,read_only=True)
      attachment = FileSerializer(many=True,read_only=True)
      class Meta:
          model = Site
          fields = ['id','site', 'project_pm', 'vendor', 'operator', 'market', 'approver', 'submitter', 'create_on', 'status', 'site_type', 'remarks', 'attachment']

I need to get the Comments made by a particular user on a particular site and the attached files. However, I am unable to get them, and I am getting no error as well. When I tried accessing SiteSerializer from Comment Serializer it worked fine, however with currently setup it is not. I am having one more model “User” as clear from the code, the User model contains User specific details. What should I try out here to make it work.

You are using nested serializer right now I can suggest you to use SerializerMethodField here like this

remarks = serializers.SerializerMethodField(read_only=True)

class Meta:
    #Your Code here

def get_remarks(self, obj):
    # Your Code here
    # You can do custom filtering and many work within this method 
    # and even use your CommentSerializer here like this..
    comment_objs = Comment.objects.filter(site=obj)
    return CommentSerializer(comment_objs, many=True).data

Try this