docs: private static void bodyWithConcatenation(
        SourceBuilder code,
        Map<Property, PropertyCodeGenerator> generatorsByProperty,
        String typename) {
      code.add("  return \"%s{", typename);
      String prefix = "";
      for (Property property : generatorsByProperty.keySet()) {
        PropertyCodeGenerator generator = generatorsByProperty.get(property);
        code.add("%s%s=\" + %s + \"",
            prefix, property.getName(), (Excerpt) generator::addToStringValue);
        prefix = ", ";
      }
      code.add("}\";%n");
    }