docs: private void toPrettyString(int indentLevel, StringBuilder buf) {
      for (int i = 0; i < indentLevel; i++) {
        buf.append("  ");
      }
      buf.append(shortName).append(": ").append(targetPatterns);
      for (GrammaticalRelation child : children) {
        buf.append('\n');
        child.toPrettyString(indentLevel + 1, buf);
      }
    }