code: func CheckSizes(key, value string) error {
  	if len(key) > MaxKeySize {
  		return ErrKeyTooLarge
  	}
  	if len(value) > MaxValueSize {
  		return ErrValueTooLarge
  	}
  	return nil
  }
docs: // CheckSizes returns ErrKeyTooLarge if key does not respect KeyMaxSize or
  // ErrValueTooLarge if value does not respect ValueMaxSize