Issue with downloaddatasubsetfromrule function

I am trying to use the function downloaddatasubsetfromrule from the plugin com.appiancorp.ps.plugins.downloaddatasubsetfromrule-2.0.0.jar.  I do not know where this plugin came from (it was in our environment when I started the project).  I am getting this error:

25 Apr 2019 16:14:21,158 INFO  [stdout] (http-0.0.0.0:8443-16) 2019-04-25 16:14:21,156 [http-0.0.0.0:8443-16] ERROR com.appiancorp.ap2.WrapFilter - javax.servlet.ServletException: JBWEB000248: Servlet execution threw an exception
25 Apr 2019 16:14:21,158 INFO  [stdout] (http-0.0.0.0:8443-16) javax.servlet.ServletException: JBWEB000248: Servlet execution threw an exception
25 Apr 2019 16:14:21,158 INFO  [stdout] (http-0.0.0.0:8443-16)  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:312)
25 Apr 2019 16:14:21,158 INFO  [stdout] (http-0.0.0.0:8443-16)  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:214)
25 Apr 2019 16:14:21,158 INFO  [stdout] (http-0.0.0.0:8443-16)  at com.appiancorp.ap2.EntryFilter.doFilter(EntryFilter.java:40)

This shows to user as a new tab when the Download link is clicked:

Here is the code to call the function:

if(
  rule!APN_isBlank(
    ri!exportUri
  ),
  a!linkField(
    links: {
      a!dynamicLink(
        label: "Export",
        saveInto: {
          a!save(
            ri!exportUri,
            fn!getdatasubsetdownloadlinkfromrule(
              rule: rule!myRule,
              input: loggedInUser()
            )
          )
        }
      )
    }
  ),
  a!linkField(
    links: {
      a!safeLink(
        label: "Download",
        uri: ri!exportUri
      )
    }
  )
)

The data coming from rule!myRule looks like this:

ExportableDataSubset
    fieldNames: List of Text String: 8 items
        "identifier"
        "title"
        "username"
        "username2"
        "group"
        "fundingStatus"
        "totalCommittedAmount"
        "createdDate"
    fieldLabels: List of Text String: 8 items
        "identifier"
        "title"
        "username"
        "username2"
        "group"
        "fundingStatus"
        "totalCommittedAmount"
        "createdDate"
    datasubset: DataSubset
        startIndex: 1
        batchSize: -1
        sort: null (List of SortInfo)
        totalCount: 370
        data: List of MyData: 370 items
        .....
    filename: "TestFile"