'Custom function that returns the list of document_ids to be sent
as attachment in email
The function may be of the form:
custom_msg_notify_attachment(resource, data, meta_data), where
resource is the S3Resource, data: the data returned from
S3Resource.select and meta_data: the meta data for the notification
(see s3notify for the metadata)'

def get_msg_notify_attachment(self):

    return self.msg.get('notify_attachment')
