diff --git a/doc/examples/example.py b/doc/examples/example.py
index ae5293af89..6c9e2f144c 100644
--- a/doc/examples/example.py
+++ b/doc/examples/example.py
@@ -4,7 +4,7 @@
 class Math:
     @staticmethod
     def fib(n: int) -> Iterator[int]:
-        """ Fibonacci series up to n """
+        """Fibonacci series up to n."""
         a, b = 0, 1
         while a < n:
             yield a