code: public static WaitStrategy fixedWait(long sleepTime, @Nonnull TimeUnit timeUnit) throws IllegalStateException {
          Preconditions.checkNotNull(timeUnit, "The time unit may not be null");
          return new FixedWaitStrategy(timeUnit.toMillis(sleepTime));
      }
docs: Returns a wait strategy that sleeps a fixed amount of time before retrying.
  
  @param sleepTime the time to sleep
  @param timeUnit  the unit of the time to sleep
  @return a wait strategy that sleeps a fixed amount of time
  @throws IllegalStateException if the sleep time is &lt; 0