code: public Retryer<R> fixedWait(long sleepTime, TimeUnit timeUnit) {
          withWaitStrategy(fixedWaitStrategy(checkNotNull(timeUnit, "TimeUnit cannot be null").toMillis(sleepTime)));
          return this;
      }
docs: Sets the wait strategy that sleeps a fixed amount of time before retrying
  
  @param sleepTime
  @param timeUnit
  @return