public static MetricRegistries load() {
    List<MetricRegistries> availableImplementations = getDefinedImplemantations();
    return load(availableImplementations);
  }
Creates a {@link MetricRegistries} instance using the corresponding {@link MetricRegistries}
available to {@link ServiceLoader} on the classpath. If no instance is found, then default
implementation will be loaded.
@return A {@link MetricRegistries} implementation.
hbase-metrics-api/src/main/java/org/apache/hadoop/hbase/metrics/MetricRegistriesLoader.java