This might be in the weeds for most folks, but the useMapperFromGraph setting in the Gremlin Server configuration file is something allowed by the serializers which let's you specify a configured graph to use to build a Mapper from that a specific serializer will use. The idea was that serializers could just get their configurations directly from a Graph instance which would bring any custom serializer stuff into Gremlin Server. The problem is that if there are multiple types of graphs then the serializers can only be configured to work with one of them.
This problem was long ago remedied with the introduction of a configuration option for serializers which would take an IoRegistry implementation directly thus allowing the user to specify multiple registries for the same serializer. I think that's ultimately the way going forward so userMapperFromGraph is a bit of an anti-pattern we are still supporting. I'd like to deprecate this feature for 3.2.6 on this ticket: https://issues.apache.org/jira/browse/TINKERPOP-1694 and then remove it completely in 3.3.0. I'll assume lazy consensus after 72 hours and proceed. Thanks, Stephen
