code: function EventStream(settings) {
      const defaults = {
          timeout: null,
          streamPath: '/notification/stream'
      };
  
      // User-provided settings from initialization
      this.settings = _.extend(defaults, settings);
      // Possible states are 'closed', 'stopped', 'started'
      this._state = 'closed';
      // Whether this is started (if so, holds the EventSource instance)
      this._eventSource = null;
  
      // Create context bindings only once, so they can be referenced when unbinding events
      this._onVisibilityStateChange = _.bind(this._onVisibilityStateChange, this);
      this._onMessage = _.bind(this._onMessage, this);
      this._onError = _.bind(this._onError, this);
  
      return _.extend(this, Backbone.Events);
  }
docs: The EventStream type wraps window.EventSource to listen to the unified
  per-user event channel endpoint using the SSE protocol. When events are
  received on the SSE channel, this triggers a Backbone event of the form
  'g:event.<type>' where <type> is the value of the event type field.
  Listeners can bind to specific event types on the channel.