text: import {Rx, Message, DatabaseStore} from 'nylas-exports';
  
  export default class ActivityDataSource {
    buildObservable({openTrackingId, linkTrackingId, messageLimit}) {
      const query = DatabaseStore
        .findAll(Message)
        .order(Message.attributes.date.descending())
        .where(Message.attributes.pluginMetadata.contains(openTrackingId, linkTrackingId))
        .limit(messageLimit);
      this.observable = Rx.Observable.fromQuery(query);
      return this.observable;
    }
  
    subscribe(callback) {
      return this.observable.subscribe(callback);
    }
  }
  