def delete(self, doc):
        if doc.id is None:
            raise DatabaseException('Document does not have id')
        if doc.sid is None:
            try:
                rs = self.db.docs.remove({'id': doc.id}, safe=True)
                assert rs['n'] == 1
            except Exception as e:
                raise DatabaseException(e)
            return None
        doc.data = None
        return self.update(doc)
def image_thumbnail(filename):
    filepath = os.path.join(app.config.get('UPLOAD_FOLDER'), filename)
    im = Image.open(filepath)
    w, h = im.size

    if w > h:
        im.thumbnail((106, 106*h/w))
    else:
        im.thumbnail((106*w/h, 106))

    im.save(os.path.join(app.config.get('UPLOAD_FOLDER'), 
        os.path.splitext(filename)[0] + '_thumbnail' + os.path.splitext(filename)[1]))