public DescribeInstancesResult unmarshall(JsonUnmarshallerContext context) throws Exception {
    DescribeInstancesResult describeInstancesResult = new DescribeInstancesResult();

    int originalDepth = context.getCurrentDepth();
    int targetDepth = originalDepth + 1;

    JsonToken token = context.currentToken;
    if (token == null) token = context.nextToken();

    while (true) {
      if (token == null) break;

      if (token == FIELD_NAME || token == START_OBJECT) {
        if (context.testExpression("Instances", targetDepth)) {
          describeInstancesResult.setInstances(
              new ListUnmarshaller<Instance>(InstanceJsonUnmarshaller.getInstance())
                  .unmarshall(context));
        }
      } else if (token == END_ARRAY || token == END_OBJECT) {
        if (context.getCurrentDepth() <= originalDepth) break;
      }

      token = context.nextToken();
    }

    return describeInstancesResult;
  }