Re narwhals-dev#1483: change isinstance(..., int) to np.isscalar(); r…

…esulting in AssertionError

narwhals/_pandas_like/series.py

@@ -18,6 +18,7 @@
 from narwhals._pandas_like.utils import select_columns_by_name
 from narwhals._pandas_like.utils import set_axis
 from narwhals._pandas_like.utils import to_datetime
+from narwhals.dependencies import get_numpy
 from narwhals.utils import Implementation
 from narwhals.utils import import_dtypes_module
 
@@ -112,7 +113,8 @@ def __getitem__(self, idx: int) -> Any: ...
     def __getitem__(self, idx: slice | Sequence[int]) -> Self: ...
 
     def __getitem__(self, idx: int | slice | Sequence[int]) -> Any | Self:
-        if isinstance(idx, int):
+        np = get_numpy()
+        if np.isscalar(idx):
             return self._native_series.iloc[idx]
         return self._from_native_series(self._native_series.iloc[idx])