Delete method applied on QuerySet calls method from DB Models

Question

Delete method applied on <class 'filer.models.filemodels.FileQuerySet'> after I filter the objects

filer_files = File.objects.filter(owner_id__in=user_ids)
filer_files.delete()

calls method from DB model

  File "/usr/local/lib/python3.6/site-packages/django/db/models/query.py", line 710, in delete
    collector.collect(del_query)
  File "/usr/local/lib/python3.6/site-packages/django/db/models/deletion.py", line 204, in collect
    parent_objs = [getattr(obj, ptr.name) for obj in new_objs]
  File "/usr/local/lib/python3.6/site-packages/django/db/models/deletion.py", line 204, in <listcomp>
    parent_objs = [getattr(obj, ptr.name) for obj in new_objs]
AttributeError: 'File' object has no attribute 'file_ptr'

instead of calling method from File class (https://github.com/django-cms/django-filer/blob/0.9/filer/models/filemodels.py#L157 )