def METHOD_NAME(self, data):
    """decrypt data"""
    try:
        plaintext = ""
        # Mocking decrypted response for tests
        if self.key == "mock":
            plaintext = "mock".encode()
        else:
            request = gkms_obj().decrypt(
                name=self.key, body={"ciphertext": base64.b64encode(data).decode("ascii")}
            )
            response = request.execute()
            plaintext = base64.b64decode(response["plaintext"].encode("ascii"))
        return plaintext.decode()
    except Exception as e:
        raise GoogleKMSError(e)