private function getValues(&$data) {
        $values = [];
        foreach ($data as $i => $row) {
            $skipImport = isset($this->skipImport) ? call_user_func($this->skipImport, $row) : false;
            if (!$skipImport) {
                foreach ($this->configs as $config) {
                    $value = call_user_func($config['value'], $row);
                    $values[$i][$config['attribute']] = $value;
                }
            }
        }
        //Filter unique values by unique attributes
        $values = $this->filterUniqueValues($values);
        return $values;
    }