code: func (s *Signer) SignBytes(c context.Context, blob []byte) (string, []byte, error) {
  	return s.Client.SignBlob(c, s.ServiceAccount, blob)
  }
docs: // SignBytes signs the blob with some active private key.
  //
  // Hashes the blob using SHA256 and then calculates RSASSA-PKCS1-v1_5 signature
  // using the currently active signing key.
  //
  // Returns the signature and name of the key used.