@Override
    public void typeCheck(AttributeValue value, Method setter) {
        if (value.getNS() == null && value.getL() == null) {
            throw new DynamoDBMappingException(
                    "Expected either L or NS in value " + value
                    + " when invoking " + setter);
        }
    }
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