code: func builtinJWTVerifyRSA(a ast.Value, b ast.Value, verify func(publicKey *rsa.PublicKey, digest []byte, signature []byte) error) (ast.Value, error) {
  	return builtinJWTVerify(a, b, func(publicKey interface{}, digest []byte, signature []byte) error {
  		publicKeyRsa, ok := publicKey.(*rsa.PublicKey)
  		if !ok {
  			return fmt.Errorf("incorrect public key type")
  		}
  		return verify(publicKeyRsa, digest, signature)
  	})
  }
docs: // Implements RSA JWT signature verification.