code: func (api *PublicWhisperAPI) AddPrivateKey(ctx context.Context, privateKey hexutil.Bytes) (string, error) {
  	key, err := crypto.ToECDSA(privateKey)
  	if err != nil {
  		return "", err
  	}
  	return api.w.AddKeyPair(key)
  }
docs: // AddPrivateKey imports the given private key.