Use shorthand attribute in threshold binary sensor (home-assistant#12…

…8612)

Small refactor threshold

homeassistant/components/threshold/binary_sensor.py

@@ -177,7 +177,6 @@ def __init__(
         self._hysteresis: float = hysteresis
         self._attr_device_class = device_class
         self._state_position = POSITION_UNKNOWN
-        self._state: bool | None = None
         self.sensor_value: float | None = None
 
     async def async_added_to_hass(self) -> None:
@@ -229,11 +228,6 @@ def async_threshold_sensor_state_listener(
         )
         _update_sensor_state()
 
-    @property
-    def is_on(self) -> bool | None:
-        """Return true if sensor is on."""
-        return self._state
-
     @property
     def extra_state_attributes(self) -> dict[str, Any]:
         """Return the state attributes of the sensor."""
@@ -261,53 +255,53 @@ def above(sensor_value: float, threshold: float) -> bool:
 
         if self.sensor_value is None:
             self._state_position = POSITION_UNKNOWN
-            self._state = None
+            self._attr_is_on = None
             return
 
         if self.threshold_type == TYPE_LOWER:
-            if self._state is None:
-                self._state = False
+            if self._attr_is_on is None:
+                self._attr_is_on = False
                 self._state_position = POSITION_ABOVE
 
             if below(self.sensor_value, self._threshold_lower):
                 self._state_position = POSITION_BELOW
-                self._state = True
+                self._attr_is_on = True
             elif above(self.sensor_value, self._threshold_lower):
                 self._state_position = POSITION_ABOVE
-                self._state = False
+                self._attr_is_on = False
             return
 
         if self.threshold_type == TYPE_UPPER:
             assert self._threshold_upper is not None
 
-            if self._state is None:
-                self._state = False
+            if self._attr_is_on is None:
+                self._attr_is_on = False
                 self._state_position = POSITION_BELOW
 
             if above(self.sensor_value, self._threshold_upper):
                 self._state_position = POSITION_ABOVE
-                self._state = True
+                self._attr_is_on = True
             elif below(self.sensor_value, self._threshold_upper):
                 self._state_position = POSITION_BELOW
-                self._state = False
+                self._attr_is_on = False
             return
 
         if self.threshold_type == TYPE_RANGE:
-            if self._state is None:
-                self._state = True
+            if self._attr_is_on is None:
+                self._attr_is_on = True
                 self._state_position = POSITION_IN_RANGE
 
             if below(self.sensor_value, self._threshold_lower):
                 self._state_position = POSITION_BELOW
-                self._state = False
+                self._attr_is_on = False
             if above(self.sensor_value, self._threshold_upper):
                 self._state_position = POSITION_ABOVE
-                self._state = False
+                self._attr_is_on = False
             elif above(self.sensor_value, self._threshold_lower) and below(
                 self.sensor_value, self._threshold_upper
             ):
                 self._state_position = POSITION_IN_RANGE
-                self._state = True
+                self._attr_is_on = True
             return
 
     @callback