public void fill(Result result, String summaryClass, Execution execution) {
        execution.fill(result, summaryClass);
    }
Fill hit properties with data using the given summary class.
Calling this on already filled results has no cost.
<p>
This needs to be overridden by <i>federating</i> searchers to contact search sources again by
propagating the fill call down through the search chain, and by <i>source</i> searchers
which talks to fill capable backends to request the data to be filled. Other searchers do
not need to override this.

@param result the result to fill
@param summaryClass the name of the collection of fields to fetch the values of, or null to use the default
container-search/src/main/java/com/yahoo/search/Searcher.java