public <U> DynamoDBTypeConverter<S,U> joinAll(DynamoDBTypeConverter<T,U> ... targets) {
            AbstractConverter<S,U> converter = (AbstractConverter<S,U>)nullSafe();
            for (DynamoDBTypeConverter<T,U> target : targets) {
                if (target != null) {
                    converter = converter.join((DynamoDBTypeConverter<U,U>)nullSafe(target));
                }
            }
            return converter;
        }
An abstract converter with additional general purpose functions.
aws-java-sdk-dynamodb/src/main/java/com/amazonaws/services/dynamodbv2/datamodeling/DynamoDBTypeConverter.java