}
    return false;
  }

  /** An implementation of {@link Map#toString}. */
  static String toStringImpl(Map<?, ?> map) {
    StringBuilder sb = Collections2.newStringBuilderForCollection(map.size()).append('{');
    boolean first = true;
    for (Entry<?, ?> entry : map.entrySet()) {
      if (!first) {
        sb.append(", ");
      }
      first = false;