Fix typo

docs/src/reference/extension_types.rst

@@ -387,7 +387,7 @@ Extension Types and None
 
 * Be very aware of exposing Python functions that take extension types as arguments::
 
-    def widen_shrubbery(Shrubbery sh, extra_width): # This is
+    def widen_shrubbery(Shrubbery sh, extra_width): # This is dangerous
     sh.width = sh.width + extra_width
 
     * Users could **crash** the program by passing ``None`` for the ``sh`` parameter.