*
   * @param labels the domain labels, from left to right.
   * @return the index of the leftmost label in the public suffix, or -1 if not found.
   */
  public int findSuffixIndex(List<String> labels) {
    return findSuffixIndex(labels, /* desiredType= */ null);
  }

  /**
   * Performs a lookup for the public suffix of the given labels and returns the index of the

    assertThat(PublicSuffixPatterns.TRIE.findSuffixIndex(ImmutableList.of("com"))).isEqualTo(0);
    assertThat(PublicSuffixPatterns.TRIE.findSuffixIndex(ImmutableList.of("google", "com")))
        .isEqualTo(1);
    assertThat(PublicSuffixPatterns.TRIE.findSuffixIndex(ImmutableList.of("abc", "google", "com")))
        .isEqualTo(2);

    assertThat(PublicSuffixPatterns.TRIE.findSuffixIndex(ImmutableList.of("co", "uk")))
        .isEqualTo(0);

    int publicSuffixIndexLocal = publicSuffixIndexCache;
    if (publicSuffixIndexLocal == SUFFIX_NOT_INITIALIZED) {
      publicSuffixIndexCache =
          publicSuffixIndexLocal = PublicSuffixPatterns.TRIE.findSuffixIndex(parts);
    }
    return publicSuffixIndexLocal;
  }

  /**
   * The index in the {@link #parts()} list at which the registry suffix begins. For example, for