Imports twitch (#28517)

* Move imports

* Add unique_id

homeassistant/components/twitch/sensor.py

 """Support for the Twitch stream status."""
 import logging
 
+from requests.exceptions import HTTPError
+from twitch import TwitchClient
 import voluptuous as vol
 
 from homeassistant.components.sensor import PLATFORM_SCHEMA
-from homeassistant.helpers.entity import Entity
 import homeassistant.helpers.config_validation as cv
+from homeassistant.helpers.entity import Entity
 
 _LOGGER = logging.getLogger(__name__)
 
@@ -14,6 +16,7 @@ ATTR_TITLE = "title"
 
 CONF_CHANNELS = "channels"
 CONF_CLIENT_ID = "client_id"
+
 ICON = "mdi:twitch"
 
 STATE_OFFLINE = "offline"
@@ -22,18 +25,16 @@ STATE_STREAMING = "streaming"
 PLATFORM_SCHEMA = PLATFORM_SCHEMA.extend(
     {
         vol.Required(CONF_CLIENT_ID): cv.string,
-        vol.Required(CONF_CHANNELS, default=[]): vol.All(cv.ensure_list, [cv.string]),
+        vol.Required(CONF_CHANNELS): vol.All(cv.ensure_list, [cv.string]),
     }
 )
 
 
 def setup_platform(hass, config, add_entities, discovery_info=None):
     """Set up the Twitch platform."""
-    from twitch import TwitchClient
-    from requests.exceptions import HTTPError
-
-    channels = config.get(CONF_CHANNELS, [])
-    client = TwitchClient(client_id=config.get(CONF_CLIENT_ID))
+    channels = config[CONF_CHANNELS]
+    client_id = config[CONF_CLIENT_ID]
+    client = TwitchClient(client_id=client_id)
 
     try:
         client.ingests.get_server_list()
@@ -55,8 +56,7 @@ class TwitchSensor(Entity):
         self._user = user
         self._channel = self._user.name
         self._id = self._user.id
-        self._state = STATE_OFFLINE
-        self._preview = self._game = self._title = None
+        self._state = self._preview = self._game = self._title = None
 
     @property
     def should_poll(self):
@@ -84,6 +84,11 @@ class TwitchSensor(Entity):
         if self._state == STATE_STREAMING:
             return {ATTR_GAME: self._game, ATTR_TITLE: self._title}
 
+    @property
+    def unique_id(self):
+        """Return unique ID for this sensor."""
+        return self._id
+
     @property
     def icon(self):
         """Icon to use in the frontend, if any."""