Getting the following error in a group by clause

[Shirshendu Shekhar Das]

I am trying to find the count of all workspaces group by Customer, and then sorting the response with the count value.

t3 = g.withSideEffect("Neptune#repeatMode","BFS")
.V().has("Project","sid","A68FA527BB214F0E9D2287B455BEFE0A8AACFED0724B407F9EBF727ED439E8ED")
.both().hasLabel("Customer").group().by().by(
both().hasLabel("Workspace").count().order().by(Column.values,Order.desc)
)
.unfold()
.project("rowName","data")
.by(select(Column.keys).properties(MandatoryCustomerAttributes.firstName.name()).value())
.by(select(Column.values))
.by(fold().unfold());

Error:

java.util.concurrent.CompletionException: org.apache.tinkerpop.gremlin.driver.exception.ResponseException: {"requestId":"c3246ac6-d306-41e6-a6d1-3adbacb928fb","code":"InvalidParameterException","detailedMessage":"The provided object does not have accessible keys: class java.lang.Long"}
    at java.util.concurrent.CompletableFuture.reportJoin(CompletableFuture.java:375)
    at java.util.concurrent.CompletableFuture.join(CompletableFuture.java:1934)
    at org.apache.tinkerpop.gremlin.driver.ResultSet.one(ResultSet.java:123)
    at org.apache.tinkerpop.gremlin.driver.ResultSet$1.hasNext(ResultSet.java:175)
    at org.apache.tinkerpop.gremlin.driver.ResultSet$1.next(ResultSet.java:182)
    at org.apache.tinkerpop.gremlin.driver.ResultSet$1.next(ResultSet.java:169)
    at org.apache.tinkerpop.gremlin.driver.remote.DriverRemoteTraversal$TraverserIterator.next(DriverRemoteTraversal.java:146)
    at org.apache.tinkerpop.gremlin.driver.remote.DriverRemoteTraversal$TraverserIterator.next(DriverRemoteTraversal.java:131)
    at org.apache.tinkerpop.gremlin.driver.remote.DriverRemoteTraversal.nextTraverser(DriverRemoteTraversal.java:112)
    at org.apache.tinkerpop.gremlin.process.remote.traversal.step.map.RemoteStep.processNextStart(RemoteStep.java:80)
    at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.next(AbstractStep.java:129)
    at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.next(AbstractStep.java:39)
    at org.apache.tinkerpop.gremlin.process.traversal.util.DefaultTraversal.next(DefaultTraversal.java:204)
    at org.apache.tinkerpop.gremlin.process.traversal.Traversal.forEachRemaining(Traversal.java:278)
    at com.callcomm.eserve.enitty.trial.NeptuneTrialCode.main(NeptuneTrialCode.java:373)