pub fn iter_pin_ref(self: Pin<&Self>) -> IterPinRef<'_, Fut> {
        let (task, len) = self.atomic_load_head_and_len_all();
        let pending_next_all = self.pending_next_all();

        IterPinRef { task, len, pending_next_all, _marker: PhantomData }
    }
Returns an iterator that allows inspecting each future in the set.
futures-util/src/stream/futures_unordered/mod.rs