* version of {@code com.google.common.base.Function} will be made to <i>extend</i> {@code
 * java.util.function.Function}, making conversion code necessary only in one direction. At that
 * time, this interface will be officially discouraged.
 *
 * @author Kevin Bourrillion
 * @since 2.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public interface Function<F extends @Nullable Object, T extends @Nullable Object>
{
  /**