*     power set size to exceed the {@code int} range)
   * @throws NullPointerException if {@code set} is or contains {@code null}
   * @see <a href="http://en.wikipedia.org/wiki/Power_set">Power set article at Wikipedia</a>
   * @since 4.0
   */
  @GwtCompatible(serializable = false)
  public static <E> Set<Set<E>> powerSet(Set<E> set) {
    return new PowerSet<E>(set);
  }

## Environment Variables

!!! tip
    If you already know what "environment variables" are and how to use them, feel free to skip to the next section below.

* 🔒 Check Content-Type request header before assuming JSON. Initial PR [#2118](https://github.com/tiangolo/fastapi/pull/2118) by [@patrickkwang](https://github.com/patrickkwang).

This change fixes a [CSRF](https://en.wikipedia.org/wiki/Cross-site_request_forgery) security vulnerability when using cookies for authentication in path operations with JSON payloads sent by browsers.