code: func FromMapKeys(m interface{}) interface{} {
  	inValue := reflect.ValueOf(m)
  	outValue := reflect.MakeSlice(reflect.SliceOf(inValue.Type().Key()), inValue.Len(), inValue.Len())
  	for i, key := range inValue.MapKeys() {
  		outValue.Index(i).Set(key)
  	}
  	return outValue.Interface()
  }
docs: // Returns all the elements []K, from m where m is map[K]T.