Craft\m160707_000000_seomatic_addGoogleTagManager::safeUp PHP Method

    public function safeUp()
    {
        // specify columns and AttributeType
        $newColumns = array('googleTagManagerID' => ColumnType::Varchar);
        $this->_addColumnsAfter("seomatic_settings", $newColumns, "googleAnalyticsUID");
        // return true and let craft know its done
        return true;
    }