code: func Int32KeySet(theMap interface{}) Int32 {
  	v := reflect.ValueOf(theMap)
  	ret := Int32{}
  
  	for _, keyValue := range v.MapKeys() {
  		ret.Insert(keyValue.Interface().(int32))
  	}
  	return ret
  }
docs: // Int32KeySet creates a Int32 from a keys of a map[int32](? extends interface{}).
  // If the value passed in is not actually a map, this will panic.