code: def _mark_image_file_stored(cls, mapper, connection, target):
          
          try:
              file_ = target.file
          except AttributeError:
              raise TypeError('sqlalchemy_imageattach.entity.Image which is '
                              'to be inserted must have file to store')
          try:
              try:
                  store = target.store
              except AttributeError:
                  raise TypeError('sqlalchemy_imageattach.entity.Image which is '
                                  'to be inserted must have store for the file')
              store.store(target, file_)
              cls._stored_images.add((target, store))
              del target.file, target.store
          finally:
              file_.close()
docs: When the session flushes, stores actual image files into
          the storage.  Note that these files could be deleted back
          if the ongoing transaction has done rollback.  See also
          :meth:`_delete_image_file()`.