public static <S,U,T> ExtendedConverter<S,U,T> join(DynamoDBTypeConverter<S,U> source, DynamoDBTypeConverter<U,T> target) {
            return new ExtendedConverter<S,U,T>(source, target);
        }
An abstract converter with additional general purpose functions.
aws-java-sdk-dynamodb/src/main/java/com/amazonaws/services/dynamodbv2/datamodeling/DynamoDBTypeConverter.java