+ ". To index multiple values under a key, use Multimaps.index.");
    }
  }

  /**
   * Creates an {@code ImmutableMap<String, String>} from a {@code Properties} instance. Properties
   * normally derive from {@code Map<Object, Object>}, but they typically contain strings, which is
   * awkward. This method lets you get a plain-old-{@code Map} out of a {@code Properties}.
   *