Refactor and edit doc string

Author: jonathanedey

firebase_admin/_messaging_encoder.py

@@ -529,10 +529,9 @@ def encode_apns(cls, apns):
                 'APNSConfig.headers', apns.headers),
             'payload': cls.encode_apns_payload(apns.payload),
             'fcm_options': cls.encode_apns_fcm_options(apns.fcm_options),
+            'live_activity_token': _Validators.check_string(
+                'APNSConfig.live_activity_token', apns.live_activity_token),
         }
-        if apns.live_activity_token:
-            result['live_activity_token'] = _Validators.check_string(
-                'APNSConfig.live_activity_token', apns.live_activity_token, non_empty=True)
         return cls.remove_null_values(result)
 
     @classmethod

firebase_admin/_messaging_utils.py

@@ -334,7 +334,7 @@ class APNSConfig:
         payload: A ``messaging.APNSPayload`` to be included in the message (optional).
         fcm_options: A ``messaging.APNSFCMOptions`` instance to be included in the message
             (optional).
-        live_activity_token: An optional string that identifies the live activity to update.
+        live_activity_token: A live activity token string (optional).
 
     .. _APNS Documentation: https://developer.apple.com/library/content/documentation\
         /NetworkingInternet/Conceptual/RemoteNotificationsPG/CommunicatingwithAPNs.html