public Store getInitializedStore(PartitionId id) {
    DiskManager diskManager = partitionToDiskManager.get(id);
    return diskManager != null ? diskManager.getInitializedStore(id) : null;
  }
@param id the {@link PartitionId} to find the store for.
@return the initialized {@link Store} corresponding to given {@link PartitionId}, or {@code null} if no store was found for
        that partition, or that store was not initialized.
ambry-store/src/main/java/com/github/ambry/store/StorageManager.java