code: public static <V> AttemptTimeLimiter<V> fixedTimeLimit(long duration, @Nonnull TimeUnit timeUnit) {
          Preconditions.checkNotNull(timeUnit);
          return new FixedAttemptTimeLimit<V>(duration, timeUnit);
      }
docs: For control over thread management, it is preferable to offer an {@link ExecutorService} through the other
  factory method, {@link #fixedTimeLimit(long, TimeUnit, ExecutorService)}. See the note on
  {@link SimpleTimeLimiter#SimpleTimeLimiter(ExecutorService)}, which this AttemptTimeLimiter uses.
  
  @param duration that an attempt may persist before being circumvented
  @param timeUnit of the 'duration' arg
  @param <V>      the type of the computation result
  @return an {@link AttemptTimeLimiter} with a fixed time limit for each attempt