Strictly type sensor.py (#56388)

homeassistant/components/tradfri/sensor.py

@@ -1,13 +1,25 @@
 """Support for IKEA Tradfri sensors."""
+from __future__ import annotations
+
+from typing import Any, Callable, cast
+
+from pytradfri.command import Command
 
 from homeassistant.components.sensor import SensorEntity
+from homeassistant.config_entries import ConfigEntry
 from homeassistant.const import DEVICE_CLASS_BATTERY, PERCENTAGE
+from homeassistant.core import HomeAssistant
+from homeassistant.helpers.entity_platform import AddEntitiesCallback
 
 from .base_class import TradfriBaseDevice
 from .const import CONF_GATEWAY_ID, DEVICES, DOMAIN, KEY_API
 
 
-async def async_setup_entry(hass, config_entry, async_add_entities):
+async def async_setup_entry(
+    hass: HomeAssistant,
+    config_entry: ConfigEntry,
+    async_add_entities: AddEntitiesCallback,
+) -> None:
     """Set up a Tradfri config entry."""
     gateway_id = config_entry.data[CONF_GATEWAY_ID]
     tradfri_data = hass.data[DOMAIN][config_entry.entry_id]
@@ -32,12 +44,16 @@ class TradfriSensor(TradfriBaseDevice, SensorEntity):
     _attr_device_class = DEVICE_CLASS_BATTERY
     _attr_native_unit_of_measurement = PERCENTAGE
 
-    def __init__(self, device, api, gateway_id):
+    def __init__(
+        self, device: Command, api: Callable[[str], Any], gateway_id: str
+    ) -> None:
         """Initialize the device."""
         super().__init__(device, api, gateway_id)
         self._attr_unique_id = f"{gateway_id}-{device.id}"
 
     @property
-    def native_value(self):
+    def native_value(self) -> int | None:
         """Return the current state of the device."""
-        return self._device.device_info.battery_level
+        if not self._device:
+            return None
+        return cast(int, self._device.device_info.battery_level)