How to use the crash.models.Crash.objects function in crash

def dispatch(self, request, *args, **kwargs):
        # verify crash_id refers to valid crash object
        try:
            self.crash = Crash.objects.select_related('crash_description').get(pk=self.kwargs.get('pk'))
        except Crash.DoesNotExist:
            return HttpResponseBadRequest('no such crash')

        # verify there is no crash description for that object yet
        try:
            desc = self.crash.crash_description
            return HttpResponseBadRequest('already reported as \"%s\"' % desc.summary)
        except ObjectDoesNotExist:
            pass

        return super(CrashDescriptionFormView, self).dispatch(request, *args, **kwargs)

class SymbolsViewSet(BaseView):
    queryset = Symbols.objects.all().order_by('-id')
    serializer_class = SymbolsSerializer

    def create(self, request, *args, **kwargs):
        try:
            return super(SymbolsViewSet, self).create(request, *args, **kwargs)
        except IntegrityError:
            res = {"message": "Duplicate symbol"}
            return Response(data=res, status=status.HTTP_409_CONFLICT)


class CrashViewSet(mixins.ListModelMixin,
                   mixins.RetrieveModelMixin,
                   viewsets.GenericViewSet):
    queryset = Crash.objects.all().order_by('-id')
    serializer_class = CrashSerializer
    pagination_class = StandardResultsSetPagination

def delete_duplicate_crashes(limit=None):
    logger = logging.getLogger('limitation')
    full_result = dict(count=0, size=0, elements=[])
    if not limit:
        preference_key = '__'.join(['Crash', 'duplicate_number'])
        limit = gpm[preference_key]
    duplicated = Crash.objects.values('signature').annotate(count=Count('signature'))
    duplicated = filter(lambda x: x['count'] > limit, duplicated)
    logger.info('Duplicated signatures: %r' % duplicated)
    for group in duplicated:
        qs = Crash.objects.filter(signature=group['signature']).order_by('created')
        dup_elements = []
        dup_count = qs.count()
        while dup_count > limit:
            bulk_size = dup_count - limit if dup_count - limit < 1000 else 1000
            bulk_ids = qs[:bulk_size].values_list('id', flat=True)
            bulk = qs.filter(id__in=bulk_ids)
            result = bulk_delete(Crash, bulk)
            full_result['count'] += result['count']
            full_result['size'] += result['size']
            full_result['elements'] += result['elements']
            dup_elements += result['elements']
            dup_count -= bulk_size

def delete_duplicate_crashes(limit=None):
    logger = logging.getLogger('limitation')
    full_result = dict(count=0, size=0, elements=[])
    if not limit:
        preference_key = '__'.join(['Crash', 'duplicate_number'])
        limit = gpm[preference_key]
    duplicated = Crash.objects.values('signature').annotate(count=Count('signature'))
    duplicated = filter(lambda x: x['count'] > limit, duplicated)
    logger.info('Duplicated signatures: %r' % duplicated)
    for group in duplicated:
        qs = Crash.objects.filter(signature=group['signature']).order_by('created')
        dup_elements = []
        dup_count = qs.count()
        while dup_count > limit:
            bulk_size = dup_count - limit if dup_count - limit < 1000 else 1000
            bulk_ids = qs[:bulk_size].values_list('id', flat=True)
            bulk = qs.filter(id__in=bulk_ids)
            result = bulk_delete(Crash, bulk)
            full_result['count'] += result['count']
            full_result['size'] += result['size']
            full_result['elements'] += result['elements']
            dup_elements += result['elements']
            dup_count -= bulk_size
    return full_result