@classmethod
def update_blob(cls, context, af_id, field_name, values):
    """Update blob info in database.

        :param context: user context
        :param af_id: id of modified artifact
        :param field_name: blob or blob dict field name
        :param values: updated blob values
        :return: updated artifact definition in Glare
        """
    af_upd = cls.db_api.update_blob(context, af_id, {field_name: values})
    return cls.init_artifact(context, af_upd)
