Entry<K, Collection<V>> entry = sortedMap().floorEntry(key);
      return (entry == null) ? null : wrapEntry(entry);
    }

    @Override
    public @Nullable K floorKey(@ParametricNullness K key) {
      return sortedMap().floorKey(key);
    }

    @Override
    public @Nullable Entry<K, Collection<V>> ceilingEntry(@ParametricNullness K key) {

        if (subRange.isEmpty()) {
          return emptyIterator();
        }
        Cut<K> cutToStart =
            MoreObjects.firstNonNull(
                entriesByLowerBound.floorKey(subRange.lowerBound), subRange.lowerBound);
        Iterator<RangeMapEntry<K, V>> backingItr =
            entriesByLowerBound.tailMap(cutToStart, true).values().iterator();