How to edit the features block in a .VMCX file (the new Hyper V config binaries)?

Question

I am attempting to make use of the Hyper V API to make changes to a virtual machine file.

Previously, when Hyper V relied on XLM files for configuration, the change in question would amount to straightforward changes in the features block. Once example of this is setting the Hyper V mode to "passthrough" as follows

<features>　
  <hyperv mode='passthrough'>
    <!-- 。。。-->
  </hyperv>
  <!-- 。。。-->
<features>　

... or, say, pass a vendor_id as follows

<features>　
  <hyperv>
    <!-- 。。。-->
    <vendor_id state='on' value='0123'/>
  </hyperv>
  <!-- 。。。-->
<features>

A Microsoft engineer does talk about editing these files in a blogpost here, accompanied by this code sample.

However, I was unable to decrypt the documentation. Does anyone now how one could go about implementing changes functionally equivalent to those described above for XML?

Thanks!