title: Unsupported property value type: java.util.LinkedHashMap when writing to Neptune
body: <p>Im using <a href="https://github.com/mpollmeier/gremlin-scala" rel="nofollow noreferrer">Gremlin-scala 3.4.1.5</a> against Neptune and I'm unable to add a vertex using a case class with a List or Set like so. Add vertex seems to work when that doesn't exist</p>
  
  <pre class="lang-scala prettyprint-override"><code>//connection
  Cluster.build()
        .addContactPoint(endpoint)
        .serializer(new GraphSONMessageSerializerV3d0())
        .port(port)
        .create()
  
  val g = EmptyGraph.instance.asScala().configure(_.withRemote(DriverRemoteConnection.using(cluster)))
  
  // adding vertex
  
  case class Person(name: String, friends: Seq[String])
  case class Person(name: String, friends: Set[String]) // also does not work
  g + Person
  </code></pre>
  
  <p><strong>Stack Trace</strong></p>
  
  <pre><code>org.apache.tinkerpop.gremlin.driver.exception.ResponseException: {"requestId":-087f-4868-b4b7-","code":"UnsupportedOperationException","detailedMessage":"Unsupported property value type: java.util.LinkedHashMap"}
  java.util.concurrent.CompletionException: org.apache.tinkerpop.gremlin.driver.exception.ResponseException: {"requestId":"-087f-4868-b4b7-","code":"UnsupportedOperationException","detailedMessage":"Unsupported property value type: java.util.LinkedHashMap"}
      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:119)
      at org.apache.tinkerpop.gremlin.driver.ResultSet$1.hasNext(ResultSet.java:171)
      at org.apache.tinkerpop.gremlin.driver.ResultSet$1.next(ResultSet.java:178)
      at org.apache.tinkerpop.gremlin.driver.ResultSet$1.next(ResultSet.java:165)
      at org.apache.tinkerpop.gremlin.driver.remote.DriverRemoteTraversal$TraverserIterator.next(DriverRemoteTraversal.java:140)
      at org.apache.tinkerpop.gremlin.driver.remote.DriverRemoteTraversal$TraverserIterator.next(DriverRemoteTraversal.java:125)
      at org.apache.tinkerpop.gremlin.driver.remote.DriverRemoteTraversal.nextTraverser(DriverRemoteTraversal.java:106)
  </code></pre>