refactor: Tiny renaming

* (refactor): An appropriate name for first parameter in classmethod in
  nodes.py module.

mypy/nodes.py

@@ -1155,7 +1155,7 @@ def serialize(self) -> JsonDict:
         }
 
     @classmethod
-    def deserialize(self, data: JsonDict) -> ClassDef:
+    def deserialize(cls, data: JsonDict) -> ClassDef:
         assert data[".class"] == "ClassDef"
         res = ClassDef(
             data["name"],