Add example for the entry for argparse
diff --git a/Doc/library/argparse.rst b/Doc/library/argparse.rst
index 63b25bb..0ca8aa0 100644
--- a/Doc/library/argparse.rst
+++ b/Doc/library/argparse.rst
@@ -1729,6 +1729,7 @@
    This method prints a usage message including the *message* to the
    standard output and terminates the program with a status code of 2.
 
+.. _upgrading-optparse-code:
 
 Upgrading optparse code
 -----------------------