@Override
        public Integer deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException, JsonProcessingException {
            return jsonParser.getIntValue();
        }
Maps in the JVM can have {@link Object} as a key, but in JSON they must be a {@link String}.
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/structure/io/graphson/GraphSONSerializersV3.java