code: func Scheme(vals ...string) {
  	ok := true
  	for _, v := range vals {
  		if v != "http" && v != "https" && v != "ws" && v != "wss" {
  			dslengine.ReportError(`invalid scheme "%s", must be one of "http", "https", "ws" or "wss"`, v)
  			ok = false
  		}
  	}
  	if !ok {
  		return
  	}
  
  	switch def := dslengine.CurrentDefinition().(type) {
  	case *design.APIDefinition:
  		def.Schemes = append(def.Schemes, vals...)
  	case *design.ResourceDefinition:
  		def.Schemes = append(def.Schemes, vals...)
  	case *design.ActionDefinition:
  		def.Schemes = append(def.Schemes, vals...)
  	default:
  		dslengine.IncompatibleDSL()
  	}
  }
docs: // Scheme can be used in: API, Resource, Action
  //
  // Scheme sets the API URL schemes.