6020 avoid creating cufile.log when import monai (#6106)

Fixes #6020

### Description

```
pip install cucim
python -c "import cucim"
```
may create a `cufile.log` file in the current working directory (please
see rapidsai/cucim#514)

this PR delays the cucim imports to when the modules are really needed. 

### Types of changes
<!--- Put an `x` in all the boxes that apply, and remove the not
applicable items -->
- [x] Non-breaking change (fix or new feature that would not break
existing functionality).
- [ ] Breaking change (fix or new feature that would cause existing
functionality to change).
- [ ] New tests added to cover the changes.
- [ ] Integration tests passed locally by running `./runtests.sh -f -u
--net --coverage`.
- [x] Quick tests passed locally by running `./runtests.sh --quick
--unittests --disttests`.
- [x] In-line docstrings updated.
- [ ] Documentation updated, tested `make html` command in the `docs/`
folder.

---------

Signed-off-by: Wenqi Li <wenqil@nvidia.com>

monai/auto3dseg/utils.py

@@ -43,7 +43,6 @@
 
 measure_np, has_measure = optional_import("skimage.measure", "0.14.2", min_version)
 cp, has_cp = optional_import("cupy")
-cucim, has_cucim = optional_import("cucim")
 
 
 def get_foreground_image(image: MetaTensor) -> np.ndarray:
@@ -93,7 +92,7 @@ def get_label_ccp(mask_index: MetaTensor, use_gpu: bool = True) -> tuple[list[An
             regardless of this setting.
 
     """
-
+    cucim, has_cucim = optional_import("cucim")
     shape_list = []
     if mask_index.device.type == "cuda" and has_cp and has_cucim and use_gpu:
         mask_cupy = ToCupy()(mask_index.short())

monai/data/image_reader.py

@@ -62,7 +62,6 @@
     nrrd, has_nrrd = optional_import("nrrd", allow_namespace_pkg=True)
 
 OpenSlide, _ = optional_import("openslide", name="OpenSlide")
-CuImage, _ = optional_import("cucim", name="CuImage")
 TiffFile, _ = optional_import("tifffile", name="TiffFile")
 
 __all__ = [
@@ -1274,7 +1273,7 @@ def _set_reader(backend: str):
         if backend == "openslide":
             return OpenSlide
         if backend == "cucim":
-            return CuImage
+            return optional_import("cucim", name="CuImage")[0]
         if backend == "tifffile":
             return TiffFile
         raise ValueError("`backend` should be 'cuCIM', 'OpenSlide' or 'TiffFile'.")

monai/data/wsi_reader.py

@@ -23,7 +23,6 @@
 from monai.data.utils import is_supported_format
 from monai.utils import WSIPatchKeys, ensure_tuple, optional_import, require_pkg
 
-CuImage, _ = optional_import("cucim", name="CuImage")
 OpenSlide, _ = optional_import("openslide", name="OpenSlide")
 TiffFile, _ = optional_import("tifffile", name="TiffFile")
 
@@ -491,13 +490,14 @@ def read(self, data: Sequence[PathLike] | PathLike | np.ndarray, **kwargs):
             whole slide image object or list of such objects
 
         """
+        cuimage_cls, _ = optional_import("cucim", name="CuImage")
         wsi_list: list = []
 
         filenames: Sequence[PathLike] = ensure_tuple(data)
         kwargs_ = self.kwargs.copy()
         kwargs_.update(kwargs)
         for filename in filenames:
-            wsi = CuImage(filename, **kwargs_)
+            wsi = cuimage_cls(filename, **kwargs_)
             wsi_list.append(wsi)
 
         return wsi_list if len(filenames) > 1 else wsi_list[0]

monai/transforms/utils.py

@@ -67,7 +67,6 @@
 ndimage, _ = optional_import("scipy.ndimage")
 cp, has_cp = optional_import("cupy")
 cp_ndarray, _ = optional_import("cupy", name="ndarray")
-cucim, has_cucim = optional_import("cucim")
 exposure, has_skimage = optional_import("skimage.exposure")
 
 __all__ = [
@@ -974,6 +973,7 @@ def get_largest_connected_component_mask(
     """
     # use skimage/cucim.skimage and np/cp depending on whether packages are
     # available and input is non-cpu torch.tensor
+    cucim, has_cucim = optional_import("cucim")
     use_cp = has_cp and has_cucim and isinstance(img, torch.Tensor) and img.device != torch.device("cpu")
     if use_cp:
         img_ = convert_to_cupy(img.short())  # type: ignore

monai/utils/module.py

@@ -477,10 +477,10 @@ def require_pkg(
     def _decorator(obj):
         is_func = isinstance(obj, FunctionType)
         call_obj = obj if is_func else obj.__init__
-        _, has = optional_import(module=pkg_name, version=version, version_checker=version_checker)
 
         @wraps(call_obj)
         def _wrapper(*args, **kwargs):
+            _, has = optional_import(module=pkg_name, version=version, version_checker=version_checker)
             if not has:
                 err_msg = f"required package `{pkg_name}` is not installed or the version doesn't match requirement."
                 if raise_error: