Issue 5754:  tweak shelve doc wording to make it clearer that even when
writeback=True values are written to the backing store when assigned to
the shelf.  Add test to confirm that this happens.  Doc patch and added
test by Robert Lehmann.  I also fixed the cross references to the sync
and close methods.
diff --git a/Lib/test/test_shelve.py b/Lib/test/test_shelve.py
index 3b20281..df56625 100644
--- a/Lib/test/test_shelve.py
+++ b/Lib/test/test_shelve.py
@@ -90,6 +90,17 @@
         self.assertEqual(len(d1), 1)
         self.assertEqual(len(d2), 1)
 
+    def test_writeback_also_writes_immediately(self):
+        # Issue 5754
+        d = {}
+        s = shelve.Shelf(d, writeback=True)
+        s['key'] = [1]
+        p1 = d['key']  # Will give a KeyError if backing store not updated
+        s['key'].append(2)
+        s.close()
+        p2 = d['key']
+        self.assertNotEqual(p1, p2)  # Write creates new object in store
+
 
 from test import mapping_tests