code: func builtinJWTVerifyRS256(a ast.Value, b ast.Value) (ast.Value, error) {
  	return builtinJWTVerifyRSA(a, b, func(publicKey *rsa.PublicKey, digest []byte, signature []byte) error {
  		return rsa.VerifyPKCS1v15(
  			publicKey,
  			crypto.SHA256,
  			digest,
  			signature)
  	})
  }
docs: // Implements RS256 JWT signature verification