code: private long getRecordsWritten() {
      long recordsWritten = 0;
      for (Optional<Fork> fork : this.forks.keySet()) {
        recordsWritten += fork.get().getRecordsWritten();
      }
      return recordsWritten;
    }
docs: Get the total number of records written by every {@link Fork}s of this {@link Task}.
  
  @return the number of records written by every {@link Fork}s of this {@link Task}