diff --git a/nvitop/api/device.py b/nvitop/api/device.py
index 6bdc546a..61d01ccf 100644
--- a/nvitop/api/device.py
+++ b/nvitop/api/device.py
@@ -189,7 +189,14 @@ def receive(self) -> int | NaType:
         return self.rx
 
 
-_VALUE_OMITTED: str = object()  # type: ignore[assignment]
+# pylint: disable-next=missing-class-docstring,too-few-public-methods
+class ValueOmitted:
+    def __repr__(self) -> str:
+        return '<VALUE OMITTED>'
+
+
+__VALUE_OMITTED: str = ValueOmitted()  # type: ignore[assignment]
+del ValueOmitted
 
 
 class Device:  # pylint: disable=too-many-instance-attributes,too-many-public-methods
@@ -499,7 +506,7 @@ def from_cuda_indices(
 
     @staticmethod
     def parse_cuda_visible_devices(
-        cuda_visible_devices: str | None = _VALUE_OMITTED,
+        cuda_visible_devices: str | None = __VALUE_OMITTED,
     ) -> list[int] | list[tuple[int, int]]:
         """Parse the given ``CUDA_VISIBLE_DEVICES`` value into a list of NVML device indices.
 
@@ -525,7 +532,7 @@ def parse_cuda_visible_devices(
         return parse_cuda_visible_devices(cuda_visible_devices)
 
     @staticmethod
-    def normalize_cuda_visible_devices(cuda_visible_devices: str | None = _VALUE_OMITTED) -> str:
+    def normalize_cuda_visible_devices(cuda_visible_devices: str | None = __VALUE_OMITTED) -> str:
         """Parse the given ``CUDA_VISIBLE_DEVICES`` value and convert it into a comma-separated string of UUIDs.
 
         This is an alias of :func:`normalize_cuda_visible_devices`.
@@ -2778,7 +2785,7 @@ def is_mig_device_uuid(uuid: str | None) -> bool:
 
 
 def parse_cuda_visible_devices(
-    cuda_visible_devices: str | None = _VALUE_OMITTED,
+    cuda_visible_devices: str | None = __VALUE_OMITTED,
 ) -> list[int] | list[tuple[int, int]]:
     """Parse the given ``CUDA_VISIBLE_DEVICES`` value into a list of NVML device indices.
 
@@ -2831,13 +2838,13 @@ def parse_cuda_visible_devices(
         >>> parse_cuda_visible_devices('16')   # invalid `CUDA_VISIBLE_DEVICES` (device ordinal out of range)
         []
     """  # pylint: disable=line-too-long
-    if cuda_visible_devices is _VALUE_OMITTED:
+    if cuda_visible_devices is __VALUE_OMITTED:
         cuda_visible_devices = os.getenv('CUDA_VISIBLE_DEVICES', default=None)
 
     return _parse_cuda_visible_devices(cuda_visible_devices, format='index')
 
 
-def normalize_cuda_visible_devices(cuda_visible_devices: str | None = _VALUE_OMITTED) -> str:
+def normalize_cuda_visible_devices(cuda_visible_devices: str | None = __VALUE_OMITTED) -> str:
     """Parse the given ``CUDA_VISIBLE_DEVICES`` value and convert it into a comma-separated string of UUIDs.
 
     This function is aliased by :meth:`Device.normalize_cuda_visible_devices`.
@@ -2888,7 +2895,7 @@ def normalize_cuda_visible_devices(cuda_visible_devices: str | None = _VALUE_OMI
         >>> normalize_cuda_visible_devices('16')    # invalid `CUDA_VISIBLE_DEVICES` (device ordinal out of range)
         ''
     """  # pylint: disable=line-too-long
-    if cuda_visible_devices is _VALUE_OMITTED:
+    if cuda_visible_devices is __VALUE_OMITTED:
         cuda_visible_devices = os.getenv('CUDA_VISIBLE_DEVICES', default=None)
 
     return ','.join(_parse_cuda_visible_devices(cuda_visible_devices, format='uuid'))
@@ -2904,14 +2911,17 @@ class _PhysicalDeviceAttrs(NamedTuple):
     support_mig_mode: bool
 
 
-_PHYSICAL_DEVICE_ATTRS = None
-_GLOBAL_PHYSICAL_DEVICE = None
-_GLOBAL_PHYSICAL_DEVICE_LOCK = threading.RLock()
+_PHYSICAL_DEVICE_ATTRS: OrderedDict[str, _PhysicalDeviceAttrs] | None = None
+_GLOBAL_PHYSICAL_DEVICE: PhysicalDevice | None = None
+_GLOBAL_PHYSICAL_DEVICE_LOCK: threading.RLock = threading.RLock()
 
 
-def _get_all_physical_device_attrs() -> dict[str, _PhysicalDeviceAttrs]:
+def _get_all_physical_device_attrs() -> OrderedDict[str, _PhysicalDeviceAttrs]:
     global _PHYSICAL_DEVICE_ATTRS  # pylint: disable=global-statement
 
+    if _PHYSICAL_DEVICE_ATTRS is not None:
+        return _PHYSICAL_DEVICE_ATTRS
+
     with _GLOBAL_PHYSICAL_DEVICE_LOCK:
         if _PHYSICAL_DEVICE_ATTRS is None:
             _PHYSICAL_DEVICE_ATTRS = OrderedDict(
@@ -3099,7 +3109,7 @@ def strip_identifier(identifier: str) -> str:
 
 
 def _parse_cuda_visible_devices_to_uuids(
-    cuda_visible_devices: str | None = _VALUE_OMITTED,
+    cuda_visible_devices: str | None = __VALUE_OMITTED,
     verbose: bool = True,
 ) -> list[str]:
     """Parse the given ``CUDA_VISIBLE_DEVICES`` environment variable in a separate process and return a list of device UUIDs.
@@ -3121,7 +3131,7 @@ def _parse_cuda_visible_devices_to_uuids(
         libcuda.CUDAError:
             If failed to parse the ``CUDA_VISIBLE_DEVICES`` environment variable.
     """  # pylint: disable=line-too-long
-    if cuda_visible_devices is _VALUE_OMITTED:
+    if cuda_visible_devices is __VALUE_OMITTED:
         cuda_visible_devices = os.getenv('CUDA_VISIBLE_DEVICES', default=None)
 
     # Do not inherit file descriptors and handles from the parent process
@@ -3138,10 +3148,7 @@ def _parse_cuda_visible_devices_to_uuids(
         parser.start()
         parser.join()
     finally:
-        try:
-            parser.kill()  # requires Python 3.7+
-        except AttributeError:
-            pass
+        parser.kill()
     result = queue.get()
 
     if isinstance(result, Exception):