code: func NewFromPEM(req *csr.CertificateRequest, keyFile string) (cert, csrPEM []byte, err error) {
  	privData, err := helpers.ReadBytes(keyFile)
  	if err != nil {
  		return nil, nil, err
  	}
  
  	priv, err := helpers.ParsePrivateKeyPEM(privData)
  	if err != nil {
  		return nil, nil, err
  	}
  
  	return NewFromSigner(req, priv)
  }
docs: // NewFromPEM creates a new root certificate from the key file passed in.