@Override
    public void writeVertex(final OutputStream outputStream, final Vertex v) throws IOException {
        writeVertex(outputStream, v, null);
    }
Writes a single {@link Vertex} with no edges serialized.

@param outputStream the stream to write to.
@param v            the vertex to write.
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/structure/io/graphson/GraphSONWriter.java