fixing example to match input cols A, B

Author: josquinlarsen

pandas/core/groupby/groupby.py

@@ -807,6 +807,7 @@ def pipe(
         pass, you can do
 
         >>> df.groupby("A").pipe(lambda x: x.max() - x.min())
+        A  B
         a  2
         b  2
         """