def METHOD_NAME(self, obj):
    """
    Method retruns query set contains all item related to concrete object.
    Example:
    >>> obj = DataCenterAsset.objects.get(id=2)
    >>> AttachmentItem.objects.get_items_for_object(obj)
    [<AttachmentItem: image/png data center asset: 2>]
    """
    content_type = get_content_type_for_model(obj)
    return self.get_queryset().select_related('attachment').filter(
        object_id=obj.pk,
        content_type=content_type,
    )