* java.util.stream.Stream#filter}. This method is not being deprecated, but we gently encourage
   * you to migrate to streams.
   */
  // TODO(kevinb): how to omit that last sentence when building GWT javadoc?
  public static <E extends @Nullable Object> Set<E> filter(
      Set<E> unfiltered, Predicate<? super E> predicate) {
    if (unfiltered instanceof SortedSet) {

      if (v instanceof Cancellation) {
        // If the other future was interrupted, clear the interrupted bit while preserving the cause
        // this will make it consistent with how non-trustedfutures work which cannot propagate the
        // wasInterrupted bit
        Cancellation c = (Cancellation) v;
        if (c.wasInterrupted) {
          v =
              c.cause != null

            catch ( SmbException e ) {
                log.debug("mkdirs", e);
                // Ignore "Cannot create a file when that file already exists." errors for now as
                // they seem to be show up under some conditions most likely due to timing issues.
                if ( e.getNtStatus() != NtStatus.NT_STATUS_OBJECT_NAME_COLLISION ) {
                    throw e;
                }
            }
        }

  }

  /**
   * A helper to create a new {@code ListenableFuture} whose result is generated from a combination
   * of input futures.
   *
   * <p>See {@link #whenAllComplete} and {@link #whenAllSucceed} for how to instantiate this class.
   *
   * <p>Example:
   *
   * <pre>{@code
   * final ListenableFuture<Instant> loginDateFuture =
   *     loginService.findLastLoginDate(username);