code: func (hm HandlerMap) Merge(other HandlerMap) {
  	for key, methods := range other {
  		if _, ok := hm[key]; !ok {
  			hm[key] = map[string]Builder{}
  		}
  		for method, builder := range methods {
  			hm[key][method] = builder
  		}
  	}
  }
docs: // Merge merges another HandlerMap into itself.