Remove unused files and code

backend/api/exceptions.py

@@ -5,8 +5,3 @@ from rest_framework.exceptions import APIException
 class LabelValidationError(APIException):
     status_code = status.HTTP_400_BAD_REQUEST
     default_detail = 'You cannot create a label with same name or shortcut key.'
-
-
-class AnnotationRelationValidationError(APIException):
-    status_code = status.HTTP_400_BAD_REQUEST
-    default_detail = 'You cannot create an annotation relation between the same annotation.'

backend/api/views/tasks/relation.py

@@ -1,37 +0,0 @@
-import json
-
-from django.db import IntegrityError, transaction
-from django.shortcuts import get_object_or_404
-from rest_framework import status
-from rest_framework.exceptions import ParseError
-from rest_framework.parsers import MultiPartParser
-from rest_framework.permissions import IsAuthenticated
-from rest_framework.response import Response
-from rest_framework.views import APIView
-
-from labels.serializers import AnnotationRelationsSerializer
-from members.permissions import IsProjectAdmin
-
-from ...exceptions import AnnotationRelationValidationError
-from ...models import Project
-
-
-class RelationUploadAPI(APIView):
-    parser_classes = (MultiPartParser,)
-    permission_classes = [IsAuthenticated & IsProjectAdmin]
-
-    @transaction.atomic
-    def post(self, request, *args, **kwargs):
-        if 'file' not in request.data:
-            raise ParseError('Empty content')
-        project = get_object_or_404(Project, pk=kwargs['project_id'])
-        try:
-            annotation_relations = json.load(request.data)
-            serializer = AnnotationRelationsSerializer(data=annotation_relations, many=True)
-            serializer.is_valid(raise_exception=True)
-            serializer.save(project=project)
-            return Response(status=status.HTTP_201_CREATED)
-        except json.decoder.JSONDecodeError:
-            raise ParseError('The file format is invalid.')
-        except IntegrityError:
-            raise AnnotationRelationValidationError