Add transactions fee to document in order printer

[Kai5x]

Hello,

Our accounting method requires a document for each transaction we make. For this matter, I started creating a template in 'order printer' to download these as PDF files. The basic invoice I'm able to create with the app isn't enough since we need to separate the transaction fees deducted from the payout from the rest. This is required for every single transaction. 

Now I'm stuck at the part of adding the line for the fee to the document. I've browsed the .dev docs provided by Shopify and found something .. I can't get it to work though. Link

I've added the following lines of code to the template but it shows nothing - not even zero as an amount:

<tr>
<td colspan="2" style="text-align: right;">Gebühren</td>
<td style="text-align: right;">{{ transactions.fee | money }}</td>
</tr>

"Gebühren" stands for fees (it's German).