Py37 fixes

Author: willmcgugan

src/textual/drivers/_byte_stream.py

@@ -2,7 +2,16 @@
 
 import io
 from collections import deque
-from typing import Callable, Deque, Generator, Generic, Iterable, NamedTuple, TypeVar
+from typing import (
+    Callable,
+    Deque,
+    Generator,
+    Generic,
+    Iterable,
+    NamedTuple,
+    Tuple,
+    TypeVar,
+)
 
 from typing_extensions import TypeAlias
 
@@ -126,7 +135,7 @@ class BytePacket(NamedTuple):
     payload: bytes
 
 
-class ByteStream(ByteStreamParser[tuple[str, bytes]]):
+class ByteStream(ByteStreamParser[Tuple[str, bytes]]):
     """A stream of packets in the following format.
 
     1 Byte for the type.