concurrently close an SSL socket. This would have appeared in crash logs as
    `NullPointerException: bio == null`.


## Version 3.12.12

_2020-05-17_

 *  Fix: Don't crash when running as a plugin in Android Studio Canary 4.1. To enable
    platform-specific TLS features OkHttp must detect whether it's running in a JVM or in Android.

      return ~~hash;
    }
  }

  /**
   * Returns the set of all possible subsets of {@code set}. For example, {@code
   * powerSet(ImmutableSet.of(1, 2))} returns the set {@code {{}, {1}, {2}, {1, 2}}}.
   *
   * <p>Elements appear in these subsets in the same iteration order as they appeared in the input
   * set. The order in which these subsets appear in the outer set is undefined. Note that the power