diff --git a/full_offline_backup_for_todoist/url_downloader.py b/full_offline_backup_for_todoist/url_downloader.py
index 9f67494..94dfab6 100644
--- a/full_offline_backup_for_todoist/url_downloader.py
+++ b/full_offline_backup_for_todoist/url_downloader.py
@@ -13,11 +13,23 @@ class URLDownloader(metaclass=ABCMeta):
     """ Implementation of a class to download the contents of an URL """
 
     _tracer: Tracer
-    __bearer_token: Optional[str]
+    _bearer_token: Optional[str]
 
     def __init__(self, tracer: Tracer):
         self._tracer = tracer
-        self.__bearer_token = None
+        self._bearer_token = None
+
+    def set_bearer_token(self, bearer_token: Optional[str]) -> None:
+        """ Sets the value of the 'Authorization: Bearer XXX' HTTP header """
+        self._bearer_token = bearer_token
+
+    @abstractmethod
+    def get(self, url: str, data: Optional[Dict[str, str]]=None) -> bytes:
+        """ Download the contents of the specified URL with a GET request.
+            You can specify any additional data parameters to pass to the destination. """
+
+class URLLibURLDownloader(URLDownloader):
+    """ Implementation of a class to download the contents of an URL through URLLib """
 
     def _download(self, opener: urllib.request.OpenerDirector, url: str,
                   data: Optional[Dict[str, str]]=None) -> bytes:
@@ -38,25 +50,13 @@ def _download_with_retry(self, opener: urllib.request.OpenerDirector, url: str,
 
         return self._download(opener, url, data)
 
-    def set_bearer_token(self, bearer_token: Optional[str]) -> None:
-        """ Sets the value of the 'Authorization: Bearer XXX' HTTP header """
-        self.__bearer_token = bearer_token
-
-    @abstractmethod
-    def get(self, url: str, data: Optional[Dict[str, str]]=None) -> bytes:
-        """ Download the contents of the specified URL with a GET request.
-            You can specify any additional data parameters to pass to the destination. """
-
     def _build_opener_with_app_useragent(
         self, *handlers: urllib.request.BaseHandler) -> urllib.request.OpenerDirector:
         opener = urllib.request.build_opener(*handlers)
         opener.addheaders = ([('User-agent', 'full-offline-backup-for-todoist')] +
-            ([('Authorization', 'Bearer ' + self.__bearer_token)] if self.__bearer_token else []))
+            ([('Authorization', 'Bearer ' + self._bearer_token)] if self._bearer_token else []))
         return opener
 
-class URLLibURLDownloader(URLDownloader):
-    """ Implementation of a class to download the contents of an URL through URLLib """
-
     def get(self, url: str, data: Optional[Dict[str, str]]=None) -> bytes:
         opener = self._build_opener_with_app_useragent()
         return self._download_with_retry(opener, url, data)