@Override
    public String wrap(String string) {
      return string;
    }
Allows to specify a custom matcher for the snapshot.
<p>
This is useful when comparing json or similar, which have less strict equality rules.

@param snapshotId      the id of the snapshot to use. In case of multiple snapshots per test, this allows to distinguish them.
@param snapshotMatcher a custom matcher for the snapshot, which is called with the snapshot value and the actual value.
                       The matcher must throw an {@link AssertionError} if the values don't match.
spock-core/src/main/java/spock/lang/Snapshotter.java