benchmarks core: fix a few mypy type errors.

benchmarks/python/core.py

@@ -62,6 +62,7 @@ def with_executor(executor: str, fwd_fn: Callable, **kwargs) -> Callable:
         )
     if executor == "thunder-torchcompile":
         return thunder.jit(fwd_fn, executors=["torchcompile"], **kwargs)
+    raise ValueError(f"Unknown executor '{executor}'")
 
 
 def compute_total_iobytes(
@@ -164,6 +165,7 @@ def torchprofile_timer(self) -> float:
 
     def fusionprofile_timer(self) -> float:
         if not self.execution_start:
+            assert self.fd is not None
             profile = self.fd.profile()
             elapsed_host_time = profile.host_time_ms / 1e3
             self._increment_global_time(elapsed_host_time)
@@ -210,7 +212,7 @@ def set_metrics(
         self,
         inputs: Union[torch.Tensor, List],
         outputs: Union[torch.Tensor, List],
-        iobytes: int = None,
+        iobytes: int | None = None,
     ) -> None:
         """
         Utility function to compute metrics for the target function.
@@ -256,9 +258,9 @@ def run_benchmark(
     benchmark: pytest_benchmark.fixture.BenchmarkFixture,
     benchmark_fn: Callable | None,
     inputs: Union[torch.Tensor, List],
-    iobytes: int = None,
+    iobytes: int | None = None,
     device: str = "cuda",
-    fusion_fn: Callable = None,
+    fusion_fn: Callable | None = None,
 ) -> Union[torch.Tensor, List]:
     """
     Benchmarks the target function using torchprofiler and stores metrics as extra information.