code: public final Ix<Boolean> all(IxPredicate<? super T> predicate) {
          return new IxAll<T>(this, nullCheck(predicate, "predicate is null"));
      }
docs: Emits true if all elements of this sequence match a given predicate (including empty).
  <p>
  The result's iterator() doesn't support remove().
  @param predicate the predicate receiving each element
  @return the new Ix instance
  @throws NullPointerException if predicate is null
  @since 1.0