docs: function _createLogger(log) {
      assert.optionalObject(log, 'log');
  
      if (log) {
          // TODO avoid this .child if already have the serializers, e.g. for
          // recursive call.
          return log.child({
              serializers: restifyClients.bunyan.serializers
          });
      } else {
          return bunyan.createLogger({
              name: 'registry',
              serializers: restifyClients.bunyan.serializers
          });
      }
  }