* Contains helper methods for string operations, including backported JDK functionality
 * for compatibility with older Java versions.
 */
public final class StringUtil {

    /**
     *
     */
    private StringUtil() {
    }

    /**
     * Implementation of {@link java.lang.String#join} backported for JDK7.
     *
     * @param delimiter the separator to use between elements

    return super.writeReplace();
  }

  @GwtIncompatible
  @J2ktIncompatible
  /*
   * The mainline copy of ImmutableMapValues doesn't produce this serialized form anymore, though
   * the backport does. For now, we're keeping the class declaration in *both* flavors so that both
   * flavors can read old data or data from the other flavor. However, we strongly discourage

### Features

* ⬆Increase supported version of aiofiles to suppress warnings. PR [#2899](https://github.com/tiangolo/fastapi/pull/2899) by [@SnkSynthesis](https://github.com/SnkSynthesis).
* ➖ Do not require backports in Python >= 3.7. PR [#1880](https://github.com/tiangolo/fastapi/pull/1880) by [@FFY00](https://github.com/FFY00).

   * @since 7.0 (source-compatible since 2.0)
   */
  // This the best we could do to get copyOfEnumSet to compile in the mainline.
  // The suppression also covers the cast to E[], discussed below.
  // In the backport, we don't have those cases and thus don't need this suppression.
  // We keep it to minimize diffs.
  @SuppressWarnings("unchecked")
  public static <E> ImmutableSet<E> copyOf(Collection<? extends E> elements) {
    /*

     * Creates a new builder. The returned builder is equivalent to the builder generated by {@link
     * ImmutableSortedSet#orderedBy}.
     */
    /*
     * TODO(cpovirk): use Object[] instead of E[] in the mainline? (The backport is different and
     * doesn't need this suppression, but we keep it to minimize diffs.) Generally be more clear
     * about when we have an Object[] vs. a Comparable[] or other array type in internalArray? If we