[unused-private-member] Handle the case using self to access members

As seen in issue pylint-dev#4644

pylint/checkers/classes.py

@@ -949,7 +949,7 @@ def _check_unused_private_variables(self, node: astroid.ClassDef) -> None:
                 if (
                     isinstance(child, astroid.Attribute)
                     and child.attrname == assign_name.name
-                    and child.expr.name in ("cls", node.name)
+                    and child.expr.name in ("self", "cls", node.name)
                 ):
                     break
             else:

tests/functional/u/unused/unused_private_member.py

@@ -87,3 +87,19 @@ def __b(cls):
     @classmethod
     def __c(cls):
         pass
+
+
+class Klass:
+    """Regression test for 4644"""
+
+    __seventyseven = 77
+    __ninetyone = 91
+
+    def __init__(self):
+        self.twentyone = 21 * (1 / (self.__seventyseven + 33)) % 100
+        self.ninetyfive = Klass.__ninetyone + 4
+
+
+k = Klass()
+print(k.twentyone)
+print(k.ninetyfive)