if (!_.isUndefined(value.model.validator) && !_.isNull(value.model.validator) &&
       _.isString(value.model.validator) && !_.isEmpty(value.model.validator)) {
      // messsage
      this.logger.debug([ '[ YMongoose.addModel ] - A validator is defined.',
                         'Try to add a validate method.' ].join(' '));