simple failing test for graph_rewrite children [pr] (tinygrad#9489)

* simple failing test for graph_rewrite children [pr]

* lint

* update too

Author: Qazalin

test/test_rewrite_tracked_childen.py

@@ -1,6 +1,7 @@
 import unittest
 from tinygrad import Tensor
-from tinygrad.ops import PatternMatcher, Ops, UPat, graph_rewrite, RewriteContext, UOp
+from tinygrad.ops import PatternMatcher, Ops, UPat, graph_rewrite, RewriteContext, UOp, merge_views
+from tinygrad.engine.schedule import sym
 
 class TestRewriteTrackedChildren(unittest.TestCase):
   def test_children_in_context(self):
@@ -47,5 +48,15 @@ def test_simple_child(self):
     print([x.arg for x in sink.get_children_map()[view_w_child]])
     self.assertSetEqual(set([x.arg for x in sink.get_children_map()[view_w_child]]), set((3,4)))
 
+  @unittest.expectedFailure
+  def test_child_after_parent_update(self):
+    def print_children(ctx, r):
+      ctx.update_children()
+      print(ctx.children[r])
+    extra = PatternMatcher([(UPat(Ops.REDUCE_AXIS, name="r"), print_children)])
+    a = Tensor.empty(3, 3)
+    r = (a+0).sum()
+    graph_rewrite(r.lazydata, merge_views+sym+extra, track_children=True)
+
 if __name__ == '__main__':
   unittest.main()