*/
  /*
   * Just as Converter could implement `Function<@Nullable A, @Nullable B>` instead of `Function<A,
   * B>`, convertAll could accept and return iterables with nullable element types. In both cases,
   * we've chosen to instead use a signature that benefits existing users -- and is still safe.
   *
   * For convertAll, I haven't looked as closely at *how* much existing users benefit, so we should

   */
  /*
   * Just as Converter could implement `Function<@Nullable A, @Nullable B>` instead of `Function<A,
   * B>`, convertAll could accept and return iterables with nullable element types. In both cases,
   * we've chosen to instead use a signature that benefits existing users -- and is still safe.
   *
   * For convertAll, I haven't looked as closely at *how* much existing users benefit, so we should