@NonNull
    public static List<Runnable> unwraps(@Nullable Collection<? extends Runnable> tasks) {
        if (tasks == null) return Collections.emptyList();

        List<Runnable> copy = new ArrayList<>();
        for (Runnable task : tasks) {
            if (!(task instanceof TtlRunnable)) copy.add(task);
            else copy.add(((TtlRunnable) task).getRunnable());
        }
        return copy;
    }
Unwrap {@link TtlRunnable} to the original/underneath one for collection.
<p>
Invoke {@link #unwrap(Runnable)} for each element in input collection.
<p>
This method is {@code null}-safe, when input {@code Runnable} parameter collection is {@code null}, return an empty list.

@see #gets(Collection)
@see #unwrap(Runnable)
ttl-core/src/main/java/com/alibaba/ttl3/TtlRunnable.java