Code beautification using f-strings (#5618)

Lib/collections/__init__.py

@@ -933,8 +933,7 @@ class ChainMap(_collections_abc.MutableMapping):
 
     @_recursive_repr()
     def __repr__(self):
-        return '{0.__class__.__name__}({1})'.format(
-            self, ', '.join(map(repr, self.maps)))
+        return f'{self.__class__.__name__}({", ".join(map(repr, self.maps))})'
 
     @classmethod
     def fromkeys(cls, iterable, *args):