code: public static WaitStrategy incrementingWait(long initialSleepTime,
                                                  @Nonnull TimeUnit initialSleepTimeUnit,
                                                  long increment,
                                                  @Nonnull TimeUnit incrementTimeUnit) {
          Preconditions.checkNotNull(initialSleepTimeUnit, "The initial sleep time unit may not be null");
          Preconditions.checkNotNull(incrementTimeUnit, "The increment time unit may not be null");
          return new IncrementingWaitStrategy(initialSleepTimeUnit.toMillis(initialSleepTime),
                  incrementTimeUnit.toMillis(increment));
      }
docs: Returns a strategy that sleeps a fixed amount of time after the first
  failed attempt and in incrementing amounts of time after each additional
  failed attempt.
  
  @param initialSleepTime     the time to sleep before retrying the first time
  @param initialSleepTimeUnit the unit of the initial sleep time
  @param increment            the increment added to the previous sleep time after each failed attempt
  @param incrementTimeUnit    the unit of the increment
  @return a wait strategy that incrementally sleeps an additional fixed time after each failed attempt