code: @Override
      public String currentLabel() {
  
          try {
              /**
               * Little bit hacky, but most concise way to do it.
               * Get the parent collection reader's current file.
               * The collection reader is basically a wrapper for a file iterator.
               * We can use this to ge the current file for the iterator.
               */
              Field f = reader.getClass().getDeclaredField("currentFile");
              f.setAccessible(true);
              File file = (File) f.get(reader);
              return file.getParentFile().getName();
          }
  
          catch (NullPointerException e1) {
              return "NONE";
          } catch (Exception e) {
              throw new RuntimeException(e);
          }
  
      }
docs: Returns the current label for nextSentence()
  
  @return the label for nextSentence()