code: CompletableFuture<Void> initialize(Duration timeout) {
          TimeoutTimer timer = new TimeoutTimer(timeout);
          Preconditions.checkState(!this.index.isInitialized(), "SegmentAttributeIndex is already initialized.");
          String attributeSegmentName = StreamSegmentNameUtils.getAttributeSegmentName(this.segmentMetadata.getName());
  
          // Attempt to open the Attribute Segment; if it does not exist yet then create it.
          return Futures
                  .exceptionallyComposeExpecting(
                          this.storage.openWrite(attributeSegmentName).thenAccept(this.handle::set),
                          ex -> ex instanceof StreamSegmentNotExistsException,
                          () -> this.storage.create(attributeSegmentName, this.config.getAttributeSegmentRollingPolicy(), timer.getRemaining()).thenAccept(this.handle::set))
                  .thenComposeAsync(v -> this.index.initialize(timer.getRemaining()), this.executor)
                  .thenRun(() -> log.debug("{}: Initialized.", this.traceObjectId))
                  .exceptionally(this::handleIndexOperationException);
      }
docs: Initializes the SegmentAttributeIndex by inspecting the AttributeSegmentFile and creating it if needed.
  
  @param timeout Timeout for the operation.
  @return A CompletableFuture that, when completed, will indicate the operation has succeeded.