public ScanSpec withNameMap(Map<String, String> nameMap) {
        if (nameMap == null)
            this.nameMap = null;
        else
            this.nameMap = Collections.unmodifiableMap(new LinkedHashMap<String, String>(nameMap));
        return this;
    }
Applicable only when an expression has been specified.
Used to specify the actual values for the attribute-name placeholders,
where the value in the map can either be string for simple attribute
name, or a JSON path expression.

@see ScanRequest#withExpressionAttributeNames(Map)
aws-java-sdk-dynamodb/src/main/java/com/amazonaws/services/dynamodbv2/document/spec/ScanSpec.java