support callback with submulti

tests/test_submulti.py

@@ -433,6 +433,20 @@ async def test_callback_submulti():
     assert not await list_sessions()
 
 
+@pytest.mark.asyncio
+async def test_callback_submulti_follower():
+    multi = StrOption('multi', '', multi=True)
+    multi2 = StrOption('multi2', '', Calculation(return_list), multi=submulti)
+    od = Leadership('multi', '', [multi, multi2])
+    od = OptionDescription('multi', '', [od])
+    async with await Config(od) as cfg:
+        await cfg.property.read_write()
+        assert await cfg.option('multi.multi').value.get() == []
+        await cfg.option('multi.multi').value.set(['val'])
+        assert await cfg.option('multi.multi2', 0).value.get() == ['val', 'val']
+    assert not await list_sessions()
+
+
 @pytest.mark.asyncio
 async def test_submulti_unique():
     i = IntOption('int', '', multi=submulti, properties=('unique',))