code: public static synchronized PushMetricRegistryInstance create(Supplier<DateTime> now, boolean has_config, EndpointRegistration api) {
          return new PushMetricRegistryInstance(now, has_config, api);
      }
docs: Create a plain, uninitialized metric registry.
  
  The metric registry is registered under its
  mbeanObjectName(package_name).
  
  @param now A function returning DateTime.now(DateTimeZone.UTC). Allowing
  specifying it, for the benefit of unit tests.
  @param has_config True if the metric registry instance should mark
  monsoon as being supplied with a configuration file.
  @param api The endpoint registration interface.
  @return An empty metric registry.