Fix all the tests failing

Author: enwask

devito/ir/iet/visitors.py

@@ -1069,10 +1069,10 @@ def __init__(self, mode: str = 'symbolics') -> None:
         if len(modes) == 1:
             self.rule = self.rules[mode]
         else:
-            self.rule = lambda n: chain(self.rules[mode](n) for mode in modes)
+            self.rule = lambda n: chain(*[self.rules[mode](n) for mode in modes])
 
     def _post_visit(self, ret):
-        return sorted(filter_ordered(ret), key=str)
+        return sorted(filter_ordered(ret, key=id), key=str)
 
     def visit_Node(self, o: Node) -> Iterator[Any]:
         yield from self._visit(o.children)