@Override
    public GraphSONSerializerProvider createInstance(final SerializationConfig config,
                                                     final SerializerFactory jsf) {
        // createInstance is called pretty often to create a new SerializerProvider
        // we give it the unknownTypeSerializer that we had in the first place,
        // when the object was first constructed through the public constructor
        // that has a GraphSONVersion.
        return new GraphSONSerializerProvider(this, config, jsf, unknownTypeSerializer);
    }
Implementation of the {@code DefaultSerializerProvider} for Jackson that uses the {@code ToStringSerializer} for
unknown types.

@author Stephen Mallette (http://stephen.genoprime.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/structure/io/graphson/GraphSONSerializerProvider.java