* SettableFuture} or one of the methods in the {@link Futures#immediateFuture Futures.immediate*}
 * family. <b>Avoid</b> creating a mock or stub {@code Future}. Mock and stub implementations are
 * fragile because they assume that only certain methods will be called and because they often
 * implement subtleties of the API improperly.
 *

   * accessed directly after this method returns. These conditions are ensured if the map is created
   * empty, passed directly to this method, and no reference to the map is retained, as illustrated
   * in the following code fragment:
   *
   * <pre>{@code
   * Set<Object> identityHashSet = Sets.newSetFromMap(
   *     new IdentityHashMap<Object, Boolean>());
   * }</pre>
   *
   * <p>The returned set is serializable if the backing map is.

 * SettableFuture} or one of the methods in the {@link Futures#immediateFuture Futures.immediate*}
 * family. <b>Avoid</b> creating a mock or stub {@code Future}. Mock and stub implementations are
 * fragile because they assume that only certain methods will be called and because they often
 * implement subtleties of the API improperly.
 *