Very much done

test.py

@@ -1,8 +1,23 @@
-from utils.Singleton import Singleton
-class A(metaclass=Singleton):
+class A:
     def __init__(self, a):
         self.a = a
     def printa(self):
         print(self.a)
+    def test2(self, _):
+        print(34)
 
+    def test3(self):
+        print(5)
 
+class B(A):
+    def test(self, fun):
+        fun(self)
+    def test3(self, a):
+        super().test3()
+        print(a)
+
+class C:
+    def __init__(self):
+        self.foo()
+    def foo(self):
+        self.a = 10