framework/data/DataFilter.php
protected function parseErrorMessage($messageKey, $params = [])
    {
        $messages = $this->getErrorMessages();
        if (isset($messages[$messageKey])) {
            $message = $messages[$messageKey];
        } else {
            $message = Yii::t('yii', 'The format of {filter} is invalid.');
        }

        $params = array_merge(
            [
                'filter' => $this->getAttributeLabel($this->filterAttributeName),
            ],
            $params
        );

        return Yii::$app->getI18n()->format($message, $params, Yii::$app->language);
    }
protected function parseErrorMessage($messageKey, $params = [])
    {
        $messages = $this->getErrorMessages();
        if (isset($messages[$messageKey])) {
            $message = $messages[$messageKey];
        } else {
            $message = Yii::t('yii', 'The format of {filter} is invalid.');
        }

        $params = array_merge(
            [
                'filter' => $this->getAttributeLabel($this->filterAttributeName),
            ],
            $params
        );

        return Yii::$app->getI18n()->format($message, $params, Yii::$app->language);
    }
Parses content of the message from [[errorMessages]], specified by message key.
@param string $messageKey message key.
@param array $params params to be parsed into the message.
@return string composed message string.