protected final void _writePrefix(Object value, JsonGenerator jgen)
     throws IOException, JsonProcessingException {
   jgen.writeStartObject();
 }
 protected final void _writeSuffix(Object value, JsonGenerator jgen)
     throws IOException, JsonProcessingException {
   jgen.writeEndObject();
   jgen.writeStringField(_typePropertyName, _idResolver.idFromValue(value));
 }