Bug in optimizer with test_model and 3+ layers

[abergeron]

Compiling a model with 3+ layers gives

@property
   def manager(self):
       “”"Return the GraphManager for this Graph.“”"
       if self._manager is None:
>           raise Exception(f’Graph {self} has no manager.’)
E           Exception: Graph 823:_graph0 has no manager.

while applying inline_trivial.

This used to work with a previous commit (but I didn't bisect to find it yet).