Fix typing and streamline code in One-Time Password integration (#118511)

* Fix some issues

* some changes

homeassistant/components/otp/sensor.py

@@ -12,7 +12,7 @@ from homeassistant.const import CONF_NAME, CONF_TOKEN
 from homeassistant.core import HomeAssistant, callback
 import homeassistant.helpers.config_validation as cv
 from homeassistant.helpers.entity_platform import AddEntitiesCallback
-from homeassistant.helpers.typing import ConfigType, DiscoveryInfoType
+from homeassistant.helpers.typing import ConfigType, DiscoveryInfoType, StateType
 
 DEFAULT_NAME = "OTP Sensor"
 
@@ -34,8 +34,8 @@ async def async_setup_platform(
     discovery_info: DiscoveryInfoType | None = None,
 ) -> None:
     """Set up the OTP sensor."""
-    name = config.get(CONF_NAME)
-    token = config.get(CONF_TOKEN)
+    name = config[CONF_NAME]
+    token = config[CONF_TOKEN]
 
     async_add_entities([TOTPSensor(name, token)], True)
 
@@ -46,34 +46,24 @@ class TOTPSensor(SensorEntity):
 
     _attr_icon = "mdi:update"
     _attr_should_poll = False
+    _attr_native_value: StateType = None
+    _next_expiration: float | None = None
 
-    def __init__(self, name, token):
+    def __init__(self, name: str, token: str) -> None:
         """Initialize the sensor."""
-        self._name = name
+        self._attr_name = name
         self._otp = pyotp.TOTP(token)
-        self._state = None
-        self._next_expiration = None
 
     async def async_added_to_hass(self) -> None:
         """Handle when an entity is about to be added to Home Assistant."""
         self._call_loop()
 
     @callback
-    def _call_loop(self):
-        self._state = self._otp.now()
+    def _call_loop(self) -> None:
+        self._attr_native_value = self._otp.now()
         self.async_write_ha_state()
 
         # Update must occur at even TIME_STEP, e.g. 12:00:00, 12:00:30,
         # 12:01:00, etc. in order to have synced time (see RFC6238)
         self._next_expiration = TIME_STEP - (time.time() % TIME_STEP)
         self.hass.loop.call_later(self._next_expiration, self._call_loop)
-
-    @property
-    def name(self):
-        """Return the name of the sensor."""
-        return self._name
-
-    @property
-    def native_value(self):
-        """Return the state of the sensor."""
-        return self._state