code: public static void throwIfUnchecked(Throwable t) {
      Preconditions.checkNotNull(t);
      if (t instanceof RuntimeException) {
        throw (RuntimeException) t;
      }
      if (t instanceof Error) {
        throw (Error) t;
      }
    }
docs: Throws {code t} if it is an instance of {@link RuntimeException} or {@link Error}.
  
  <p>This is intended to mimic Guava's method by the same name, but which is unavailable to us
  due to compatibility with older Guava versions.