public Snapshotter normalizedWith(Function<String, String> normalizer) {
    Checks.notNull(normalizer, () -> "normalizer is null");
    this.normalizer = normalizer;
    return this;
  }
Declares a {@link Function} for normalizing the reference value.
<p>
The default normalization is line ending normalization.
spock-core/src/main/java/spock/lang/Snapshotter.java