String getPrimaryRangeKeyName(Class<?> clazz) {
        Method primaryRangeKeyGetter = getPrimaryHashKeyGetter(clazz);
        return primaryRangeKeyGetter == null ?
                null
                :
                getAttributeName(getPrimaryRangeKeyGetter(clazz));
    }
Returns the name of the primary range key, or null if the table does not
one.
aws-java-sdk-dynamodb/src/main/java/com/amazonaws/services/dynamodbv2/datamodeling/DynamoDBReflector.java