Apply suggestions from code review

Co-authored-by: Alex Waygood <[email protected]>

Author: srittau

src/test_typing_extensions.py

@@ -4113,8 +4113,8 @@ class WrongReader:
             def readx(self, n: int) -> bytes:
                 return b""
 
-        assert isinstance(MyReader(), typing_extensions.Reader)
-        assert not isinstance(WrongReader(), typing_extensions.Reader)
+        self.assertIsInstance(MyReader(), typing_extensions.Reader)
+        self.assertNotIsInstance(WrongReader(), typing_extensions.Reader)
 
     def test_writer_runtime_checkable(self):
         class MyWriter:
@@ -4125,8 +4125,8 @@ class WrongWriter:
             def writex(self, b: bytes) -> int:
                 return 0
 
-        assert isinstance(MyWriter(), typing_extensions.Writer)
-        assert not isinstance(WrongWriter(), typing_extensions.Writer)
+        self.assertIsInstance(MyWriter(), typing_extensions.Writer)
+        self.assertNotIsInstance(WrongWriter(), typing_extensions.Writer)
 
 
 class Point2DGeneric(Generic[T], TypedDict):

src/typing_extensions.py

@@ -884,8 +884,6 @@ def write(self, data: T_contra, /) -> int:
             """Write data to the output stream and return the number of items written."""
 
 
-
-
 _NEEDS_SINGLETONMETA = (
     not hasattr(typing, "NoDefault") or not hasattr(typing, "NoExtraItems")
 )