@Override
        public DataList<DATATYPE> getOwner() {
            return owner;
        }
Creates a null implementation of this which is empty and complete at creation:
<ul>
<li>Provides immediate return without incurring any memory synchronization for
any read method.
<li>Throws an exception on any write method
</ul>
<p>
This allows consumers to check for completion the same way whether or not the data list in question
supports asynchronous addition of data, and without incurring unnecessary costs.
container-core/src/main/java/com/yahoo/processing/response/IncomingData.java