Why won't this django-rest-swagger API documentation display/work properly?

I tested this with cigar_example which is made by django-rest-swagger and in that example they written one custom view which is also not rendering input parameters

Lastly i look into source code and found that django-rest-swagger needs get_serializer_class to build body parameters

So it worked with the following code:

class isEmailTaken(views.APIView):
    permission_classes = [permissions.AllowAny,]
    serializer_class = IsEmailTakenSerializer

    def get_serializer_class(self):
        return self.serializer_class

    def post(self, request, *args, **kwargs):
        try:
            email = request.DATA['email']
        except KeyError:
            return HttpResponse(
               'An email was not given with this request.', 
                status=status.HTTP_400_BAD_REQUEST,
            )
        return HttpResponse(
            json.dumps(
                User.objects.filter(email=email), 
                content_type="application/json",
                status=status.HTTP_200_OK,
             )
         )

and IsEmailTakenSerializer:

from rest_framework import serializers


class IsEmailTakenSerializer(serializers.Serializer):
    email = serializers.EmailField()