Fix mypy error in cutlass_gemm example

Author: oleksandr-pavlyk

python/examples/cutlass_gemm.py

@@ -34,9 +34,11 @@ def as_core_Stream(cs: nvbench.CudaStream) -> core.Stream:
     return core.Stream.from_handle(cs.addressof())
 
 
-def make_cp_array(arr_h: np.ndarray, dev_buf: core.Buffer, dev_id: int) -> cp.ndarray:
+def make_cp_array(
+    arr_h: np.ndarray, dev_buf: core.Buffer, dev_id: int | None
+) -> cp.ndarray:
     cp_memview = cp.cuda.UnownedMemory(
-        int(dev_buf.handle), dev_buf.size, dev_buf, dev_id
+        int(dev_buf.handle), dev_buf.size, dev_buf, -1 if dev_id is None else dev_id
     )
     zero_offset = 0
     return cp.ndarray(