code: public void removePolledDirectory(PolledDirectory directory) {
          if (directory == null) {
              throw new NullPointerException(NULL_ARGUMENT_ERROR);
          }
          scheduledRunnable.removeDirectory(directory);
      }
docs: Removes the given <code>directory</code> from this instance.
  The <code>directory</code> will be removed after any ongoing
  poll-cycles has finished. If there's no ongoing poll-cycles,
  then the given <code>directory</code> will be removed just before
  next poll-cycle is started.
  
  @param directory implementation of {@link PolledDirectory}.
  @throws NullPointerException if the given argument is null.