public @Nullable V get(@Nullable Object key) {
      if (key instanceof Range) {
        Range<?> range = (Range<?>) key;
        RangeMapEntry<K, V> rangeMapEntry = entriesByLowerBound.get(range.lowerBound);
        if (rangeMapEntry != null && rangeMapEntry.getKey().equals(range)) {
          return rangeMapEntry.getValue();
        }
      }
      return null;
    }

    @Override
    public int size() {