ListenableFuture<? extends V>... futures) {
    ListenableFuture<List<@Nullable V>> nullable =
        new ListFuture<V>(ImmutableList.copyOf(futures), true);
    // allAsList ensures that it fills the output list with V instances.
    @SuppressWarnings("nullness")
    ListenableFuture<List<V>> nonNull = nullable;
    return nonNull;
  }

  /**

_2016-05-24_

 *  New: `Response.sentRequestAtMillis()` and `receivedResponseAtMillis()`
    methods track the system's local time when network calls are made. These
    replace the `OkHttp-Sent-Millis` and `OkHttp-Received-Millis` headers that were
    present in earlier versions of OkHttp.
 *  New: Accept user-provided trust managers in `OkHttpClient.Builder`. This
    allows OkHttp to satisfy its TLS requirements directly. Otherwise OkHttp