code: function initSingleton() {
      var instance;
      if (instances.length) {
          instance = instances.filter(function(item) {
              return item.name === "singleton";
          });
          if (instance.length) {
              logger.error(
                  "{yellow:You tried to start Browsersync twice!} To create multiple instances, use {cyan:browserSync.create().init()"
              );
              return instance;
          }
      }
      var args = Array.prototype.slice.call(arguments);
      singleton = create("singleton", getSingletonEmitter());
  
      if (singletonPlugins.length) {
          singletonPlugins.forEach(function(obj) {
              singleton.instance.registerPlugin.apply(
                  singleton.instance,
                  obj.args
              );
          });
      }
  
      singleton.init.apply(null, args);
      return singleton;
  }
docs: Create a single instance when module export is used directly via browserSync({});
  This is mostly for back-compatibility, for also for the nicer api.
  This will never be removed to ensure we never break user-land, but
  we should discourage it's use.
  @returns {*}