Unofficial package

I am new to Weka and am currently using the 3.9.5 version, I wanna try an algorithm for pre-processing called Knn-undersampling, It is not available on weka packages since it was made by a researcher for their research(they also installed this in weka for their study), I wanna install that algorithm to weka, however i get this error messages when i try to install 

java.lang.Exception: Unable to find Description file in package archive!
	at weka.core.packageManagement.DefaultPackageManager.getPackageArchiveInfo(DefaultPackageManager.java:371)
	at weka.core.WekaPackageManager.installPackageFromArchive(WekaPackageManager.java:2337)
	at weka.gui.PackageManager$UnofficialInstallTask.doInBackground(PackageManager.java:780)
	at weka.gui.PackageManager$UnofficialInstallTask.doInBackground(PackageManager.java:724)
	at java.desktop/javax.swing.SwingWorker$1.call(Unknown Source)
	at java.base/java.util.concurrent.FutureTask.run(Unknown Source)
	at java.desktop/javax.swing.SwingWorker.run(Unknown Source)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	at java.base/java.lang.Thread.run(Unknown Source)

The Algorithm can be found in github repository : https://github.com/marcelobeckmann/knnund
Can someone help me on how to install this on weka?
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