code: function LocalIndexedDBStoreBackend(
      indexedDBInterface, dbName,
  ) {
      this.indexedDB = indexedDBInterface;
      this._dbName = "matrix-js-sdk:" + (dbName || "default");
      this.db = null;
      this._disconnected = true;
      this._syncAccumulator = new SyncAccumulator();
      this._isNewlyCreated = false;
  }
docs: Does the actual reading from and writing to the indexeddb
  
  Construct a new Indexed Database store backend. This requires a call to
  <code>connect()</code> before this store can be used.
  @constructor
  @param {Object} indexedDBInterface The Indexed DB interface e.g
  <code>window.indexedDB</code>
  @param {string=} dbName Optional database name. The same name must be used
  to open the same database.