Pluggable widget XML definition

Since I am having some issues with defining the xml file, I was wondering is the xsd file available to which the widget.xml files is validated against? Edit: To be more specific, i am trying to add an reference set association to the xml but this fails with the following error Widget XML file 'AutocompleteMultiselect.xml' does not conform to the XML schema: The 'name' attribute is invalid - The value 'ReferenceSet' is invalid according to its datatype '' - The Enumeration constraint failed. Even though the specification claims it should be ReferenceSet.
1 answers

I just noticed something in the specs:

And I see you’re on version 9.12.2