add a space after if, and put curly braces even for one line expressions for if/else. i.e.

```scala
if (withReplacement) {
  new IndependentlySampledRDD[T, T](this, new PoissonSampler[T](fraction), seed)
} else {
  new IndependentlySampledRDD[T, T](this, new BernoulliSampler[T](fraction), seed)
}
```