public function getEstimatedWeight($i = 0,$mode = 0){
        if (!isset($this->previewList)){
            return false;
        }
        if (is_int($i) && $i >= 0){
            if ($mode == 1){
                return $this->previewList[$i]['EstimatedShippingWeight']['Unit'];
            } else if ($mode == 2){
                return $this->previewList[$i]['EstimatedShippingWeight'];
            } else 
            {
                return $this->previewList[$i]['EstimatedShippingWeight']['Value'];
            }
        } else {
            return false;
        }
    }