code: func validateDataIntegrity(k []byte, expectedSize int) bool {
  	if len(k) != expectedSize {
  		return false
  	}
  	if expectedSize > 3 && containsOnlyZeros(k) {
  		return false
  	}
  	return true
  }
docs: // validateDataIntegrity returns false if the data have the wrong or contains all zeros,
  // which is the simplest and the most common bug.