Use TYPE_CHECKING to work around python 3.8 limitations with generics (…

…#18152)

* Use TYPE_CHECKING to work around python 3.8 limitations with generics

* Add comment about 3.8 specific workaround

chia/_tests/wallet/test_new_wallet_protocol.py

@@ -3,7 +3,7 @@
 from asyncio import Queue
 from dataclasses import dataclass
 from random import Random
-from typing import AsyncGenerator, Dict, List, Optional, OrderedDict, Set, Tuple
+from typing import TYPE_CHECKING, AsyncGenerator, Dict, List, Optional, OrderedDict, Set, Tuple
 
 import pytest
 from chia_rs import AugSchemeMPL, Coin, CoinSpend, CoinState, Program
@@ -33,6 +33,11 @@
 IDENTITY_PUZZLE_HASH = IDENTITY_PUZZLE.get_tree_hash()
 
 OneNode = Tuple[List[SimulatorFullNodeService], List[WalletService], BlockTools]
+# python 3.8 workaround follows - can be removed when 3.8 support is removed
+if TYPE_CHECKING:
+    Mpu = Tuple[FullNodeSimulator, Queue[Message], WSChiaConnection]
+else:
+    Mpu = Tuple[FullNodeSimulator, Queue, WSChiaConnection]
 
 ALL_FILTER = wallet_protocol.CoinStateFilters(True, True, True, uint64(0))
 
@@ -798,9 +803,6 @@ async def assert_mempool_removed(
     assert set(update.removed_items) == removed_items
 
 
-Mpu = Tuple[FullNodeSimulator, Queue[Message], WSChiaConnection]
-
-
 @pytest.fixture
 async def mpu_setup(one_node: OneNode, self_hostname: str) -> Mpu:
     return await raw_mpu_setup(one_node, self_hostname)