code: func NewSigner(conf Config) (*Signer, error) {
  	sId, err := serializeIdentity(conf.IdentityPath, conf.MSPID)
  	if err != nil {
  		return nil, errors.WithStack(err)
  	}
  	key, err := loadPrivateKey(conf.KeyPath)
  	if err != nil {
  		return nil, errors.WithStack(err)
  	}
  	return &Signer{
  		Creator: sId,
  		key:     key,
  	}, nil
  }
docs: // NewSigner creates a new Signer out of the given configuration