refactor: use __all__ in accelerators/__init__.py (#20889)

Author: littlebullGit

src/lightning/pytorch/accelerators/__init__.py

@@ -10,16 +10,26 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+
+__all__ = [
+    "Accelerator",
+    "CPUAccelerator",
+    "CUDAAccelerator",
+    "MPSAccelerator",
+    "XLAAccelerator",
+    "find_usable_cuda_devices",
+]
+
 import sys
 
-from lightning.fabric.accelerators import find_usable_cuda_devices  # noqa: F401
+from lightning.fabric.accelerators import find_usable_cuda_devices
 from lightning.fabric.accelerators.registry import _AcceleratorRegistry
 from lightning.fabric.utilities.registry import _register_classes
 from lightning.pytorch.accelerators.accelerator import Accelerator
-from lightning.pytorch.accelerators.cpu import CPUAccelerator  # noqa: F401
-from lightning.pytorch.accelerators.cuda import CUDAAccelerator  # noqa: F401
-from lightning.pytorch.accelerators.mps import MPSAccelerator  # noqa: F401
-from lightning.pytorch.accelerators.xla import XLAAccelerator  # noqa: F401
+from lightning.pytorch.accelerators.cpu import CPUAccelerator
+from lightning.pytorch.accelerators.cuda import CUDAAccelerator
+from lightning.pytorch.accelerators.mps import MPSAccelerator
+from lightning.pytorch.accelerators.xla import XLAAccelerator
 
 AcceleratorRegistry = _AcceleratorRegistry()
 _register_classes(AcceleratorRegistry, "register_accelerators", sys.modules[__name__], Accelerator)