GraphBinaryMessageSerializer cannot serialize DefaultComputerResult

When I send the following request to gremlin-server, I got an error "Serializer for type org.apache.tinkerpop.gremlin.process.computer.util.DefaultComputerResult not found".

graph = GraphFactory.open('conf/fdb-psave-export.properties')
graph.compute(SparkGraphComputer).program(CloneVertexProgram.build().create()).submit().get()

After investigation, I found GraphBinaryMessageSerializer cannot serialize DefaultComputerResult. The quick workaround is change the gremline to

graph = GraphFactory.open('conf/fdb-psave-export.properties')
a= graph.compute(SparkGraphComputer).program(CloneVertexProgram.build().create()).submit().get()
a.toString()

This asks the GraphBinaryMessageSerializer to serialize String instead of DefaultComputerGraph.

I'm wondering is it possible to change the GraphBinaryMessageSerializer to automatically handle this.