private Set<Boolean> unmarshallNS(List<String> values) {
        Set<Boolean> result = new HashSet<Boolean>();

        for (String s : values) {
            if ("1".equals(s)) {
                result.add(Boolean.TRUE);
            } else if ("0".equals(s)) {
                result.add(Boolean.FALSE);
            } else {
                throw new IllegalArgumentException(
                        "Expected '1' or '0' for boolean value, was " + s);
            }
        }

        return result;
    }
A special unmarshaller for Set&lt;Boolean>, which the V1 schema stores as
an NS using 0/1 for true/false. In the V2 schema these fall through to
the {@code ObjectSetToListMarshaller} which stores them as an L or BOOLs.
aws-java-sdk-dynamodb/src/main/java/com/amazonaws/services/dynamodbv2/datamodeling/unmarshallers/BooleanSetUnmarshaller.java