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