private Metric.Context createRelevanceMetricContext(String chainName, String rankProfile) {
        Map<String, String> dimensions = new HashMap<>();
        dimensions.put("chain", chainName);
        dimensions.put("rankProfile", rankProfile);
        return metric.createContext(dimensions);
    }
<p>A searcher to gather statistics such as queries completed and query latency.  There
may be more than 1 StatisticsSearcher in the Searcher chain, each identified by a
Searcher ID.  The statistics accumulated by all StatisticsSearchers are stored
in the singleton StatisticsManager object. </p>
<p>
TODO: Fix events to handle more than one of these searchers properly.

@author Gene Meyers
@author Steinar Knutsen
@author bergum
container-search/src/main/java/com/yahoo/prelude/statistics/StatisticsSearcher.java