I found out in the source code of the model [(here is the line](https://github.com/GreenDelta/olca-modules/blob/806a11d11fc4e96020b01015648cac53475d1c49/olca-core/src/main/java/org/openlca/core/model/Exchange.java#L30)) that the proper name of the attribute was `isInput`. Both the olca-schema doc and the README of this repo indicate `input` : 
I found out in the source code of the model (here is the line) that the proper name of the attribute was
isInput.Both the olca-schema doc and the README of this repo indicate
input: