@webapi_check_local_site
    @webapi_login_required
    @webapi_response_errors(DOES_NOT_EXIST, INVALID_FORM_DATA,
                            NOT_LOGGED_IN, PERMISSION_DENIED)
    @webapi_request_fields(
        required=dict({
            'filediff_id': {
                'type': int,
                'description': 'The ID of the file diff the comment is on.',
            },
            'first_line': {
                'type': int,
                'description': 'The line number the comment starts at.',
            },
            'num_lines': {
                'type': int,
                'description': 'The number of lines the comment spans.',
            },
        }, **BaseDiffCommentResource.REQUIRED_CREATE_FIELDS),
        optional=dict({
            'interfilediff_id': {
                'type': int,
                'description': 'The ID of the second file diff in the '
                               'interdiff the comment is on.',
            },
        }, **BaseDiffCommentResource.OPTIONAL_CREATE_FIELDS),
        allow_unknown=True,
    )
    def create(self, request, filediff_id, interfilediff_id=None,
               *args, **kwargs):
        try:
            review_request = \
                resources.review_request.get_object(request, *args, **kwargs)
            review = resources.review.get_object(request, *args, **kwargs)
        except ObjectDoesNotExist:
            return DOES_NOT_EXIST

        if not resources.review.has_modify_permissions(request, review):
            return self.get_no_access_error(request)

        filediff = None
        interfilediff = None
        invalid_fields = {}

        try:
            filediff = FileDiff.objects.get(
                pk=filediff_id,
                diffset__history__review_request=review_request)
        except ObjectDoesNotExist:
            invalid_fields['filediff_id'] = \
                ['This is not a valid filediff ID']

        if filediff and interfilediff_id:
            if interfilediff_id == filediff.id:
                invalid_fields['interfilediff_id'] = \
                    ['This cannot be the same as filediff_id']
            else:
                try:
                    interfilediff = FileDiff.objects.get(
                        pk=interfilediff_id,
                        diffset__history=filediff.diffset.history)
                except ObjectDoesNotExist:
                    invalid_fields['interfilediff_id'] = \
                        ['This is not a valid interfilediff ID']

        if invalid_fields:
            return INVALID_FORM_DATA, {
                'fields': invalid_fields,
            }

        new_comment = self.create_comment(
            review=review,
            filediff=filediff,
            interfilediff=interfilediff,
            fields=('filediff', 'interfilediff', 'first_line', 'num_lines'),
            **kwargs)
        review.comments.add(new_comment)

        return 201, {
            self.item_result_key: new_comment,
        }
Creates a new diff comment.
dataset/ETHPy150Open reviewboard/reviewboard/reviewboard/webapi/resources/review_diff_comment.py/ReviewDiffCommentResource.create