title: What will DynamoDB Mapper batchLoad return if no items exist?
body: <p>I'm sure for DynamoDBMapper.load(), if try to query database but find nothing it will return null.</p>
  
  <p>But what about DynamoDBMapper.batchLoad()? 
  public Map> batchLoad(Iterable itemsToGet)</p>
  
  <p>The documentation only saying:
  A map of the loaded objects. Each key in the map is the name of a DynamoDB table. Each value in the map is a list of objects that have been loaded from that table. All objects for each table can be cast to the associated user defined type that is annotated as mapping that table.</p>
  
  <p>So I guess it won't return null, but an empty Map or even Empty List?</p>