code: @Nullable
      public static Runnable unwrap(@Nullable Runnable runnable) {
          if (!(runnable instanceof TtlRunnable)) return runnable;
          else return ((TtlRunnable) runnable).getRunnable();
      }
docs: Unwrap {@link TtlRunnable} to the original/underneath one.
  <p>
  this method is {@code null}-safe, when input {@code Runnable} parameter is {@code null}, return {@code null};
  if input {@code Runnable} parameter is not a {@link TtlRunnable} just return input {@code Runnable}.
  <p>
  so {@code TtlRunnable.unwrap(TtlRunnable.get(runnable))} will always return the same input {@code runnable} object.
  
  @see #get(Runnable)
  @since 2.10.2