def save(self, doc):
        if doc.id:
            return self.update(doc)
        else:
            return self.insert(doc)
def image_delete(filename):
    thumbnail_filepath = os.path.join(app.config.get('UPLOAD_FOLDER'), filename)
    filepath = thumbnail_filepath.replace('_thumbnail', '')
    os.remove(filepath)
    os.remove(thumbnail_filepath)