[Bugfix] Fix mock.patch resolution failure for standalone_compile.FakeTensorMode on Python <= 3.10

vllm/compilation/compiler_interface.py

@@ -373,8 +373,15 @@ class InductorStandaloneAdaptor(CompilerInterface):
                 break
 
         if input_fake_mode is not None:
-            fake_mode_ctx: Any = patch(
-                "torch._inductor.standalone_compile.FakeTensorMode",
+            # Use patch.object on the actual module from sys.modules
+            # because in Python <=3.10 the string-based patch() resolves
+            # torch._inductor.standalone_compile to the wrapper function
+            # (defined in __init__.py) instead of the module.
+            import sys
+
+            fake_mode_ctx: Any = patch.object(
+                sys.modules["torch._inductor.standalone_compile"],
+                "FakeTensorMode",
                 lambda *a, **kw: input_fake_mode,
             )
         else: