fix singleton typeing and __init__

src/libs/singleton.py

@@ -1,4 +1,5 @@
 # Python imports
+from typing import Type, TypeVar, Any
 
 # Lib imports
 
@@ -11,10 +12,12 @@ class SingletonError(Exception):
 
 
 
+T = TypeVar('T', bound='Singleton')
+
 class Singleton:
     _instance = None
 
-    def __new__(cls, *args, **kwargs):
+    def __new__(cls: Type[T], *args: Any, **kwargs: Any) -> T:
         if cls._instance is not None:
             logger.debug(f"'{cls.__name__}' is a Singleton. Returning  instance...")
             return cls._instance
@@ -22,7 +25,7 @@ class Singleton:
         cls._instance = super(Singleton, cls).__new__(cls)
         return cls._instance
 
-    def __init__(self):
+    def __init__(self) -> None:
         if self._instance is not None:
             return