code: func (r Rectangle) In(s Rectangle) bool {
  	if r.Empty() {
  		return true
  	}
  	// Note that r.Max is an exclusive bound for r, so that r.In(s)
  	// does not require that r.Max.In(s).
  	return s.Min[0] <= r.Min[0] && r.Max[0] <= s.Max[0] &&
  		s.Min[1] <= r.Min[1] && r.Max[1] <= s.Max[1]
  }
docs: // In reports whether Rectangle r is contained in s.