docstr: Verify deserialization of old-style encoded Xcom values including nested ones
docstr_tok: ["Verify","deserialization","of","old-style","encoded","Xcom","values","including","nested","ones"]
code: def test_backwards_compat(self):
      """
      Verify deserialization of old-style encoded Xcom values including nested ones
      """
      uri = "s3://does_not_exist"
      data = {
          "__type": "airflow.datasets.Dataset",
          "__source": None,
          "__var": {
              "__var": {
                  "uri": uri,
                  "extra": {
                      "__var": {"hi": "bye"},
                      "__type": "dict",
                  },
              },
              "__type": "dict",
          },
      }
      dataset = deserialize(data)
      assert dataset.extra == {"hi": "bye"}
      assert dataset.uri == uri
  
imports: from __future__ import annotations
  import datetime
  import enum
  from dataclasses import dataclass
  from importlib import import_module
  from typing import ClassVar
  import attr
  import pytest
  from pydantic import BaseModel
  from airflow.datasets import Dataset
  from airflow.serialization.serde import CLASSNAME, DATA, SCHEMA_ID, VERSION, _get_patterns, _match, deserialize, serialize
  from airflow.utils.module_loading import import_string, iter_namespace, qualname
  from tests.test_utils.config import conf_vars
label_desc: Use image node_id 14 for calling the TestSerDe obj's underlying member method code with example usage: obj.test_backwards_compat() without return types