code: func (whisper *Whisper) DeleteKeyPair(key string) bool {
  	whisper.keyMu.Lock()
  	defer whisper.keyMu.Unlock()
  
  	if whisper.privateKeys[key] != nil {
  		delete(whisper.privateKeys, key)
  		return true
  	}
  	return false
  }
docs: // DeleteKeyPair deletes the specified key if it exists.