code: func NewSignatureHeaderOrPanic(signer crypto.LocalSigner) *cb.SignatureHeader {
  	if signer == nil {
  		panic(errors.New("invalid signer. cannot be nil"))
  	}
  
  	signatureHeader, err := signer.NewSignatureHeader()
  	if err != nil {
  		panic(fmt.Errorf("failed generating a new SignatureHeader: %s", err))
  	}
  	return signatureHeader
  }
docs: // NewSignatureHeaderOrPanic returns a signature header and panics on error.