documentation added, black linter added

sources/manager_localization.py

@@ -7,19 +7,37 @@ from manager_environment import EnvironmentManager as EM
 
 def init_localization_manager():
     """
+    Initialize localization manager.
+    Load GUI translations JSON file.
     """
     LocalizationManager.load_localization("translation.json")
 
 
 class LocalizationManager:
+    """
+    Class for handling localization (and maybe other file IO in future).
+    Stores localization in dictionary.
+    """
+
     _LOCALIZATION: Dict[str, str] = dict()
 
     @staticmethod
     def load_localization(file: str):
-        with open(join(dirname(__file__), file), encoding='utf-8') as config_file:
+        """
+        Read localization file and store locale defined with environmental variable.
+
+        :param file: Localization file path, related to current file (in sources root).
+        """
+        with open(join(dirname(__file__), file), encoding="utf-8") as config_file:
             data = load(config_file)
         LocalizationManager._LOCALIZATION = data[EM.LOCALE]
 
     @staticmethod
     def t(key: str) -> str:
+        """
+        Translate string to current localization.
+
+        :param key: Localization key.
+        :returns: Translation string.
+        """
         return LocalizationManager._LOCALIZATION[key]