code: func (rs RuleSet) Merge(other RuleSet) RuleSet {
  	result := NewRuleSet()
  	for i := range rs {
  		result.Add(rs[i])
  	}
  	for i := range other {
  		result.Add(other[i])
  	}
  	return result
  }
docs: // Merge returns a ruleset containing the union of rules from rs an other.