code: func BytesFilter(f func(byte) bool, data []byte) []byte {
  	result := make([]byte, 0, 0)
  	for _, element := range data {
  		if f(element) {
  			result = append(result, element)
  		}
  	}
  	return result
  }
docs: // BytesFilter filters out all bytes where the function does not return true.