Fix CPU MLX shim: drop duplicate Module.children/__contains__ (#938)

#934 added a structure-preserving Module.children() (non-Module list/dict
items map to {}) plus a vars-based __contains__, along with the smoke test that
pins that behavior. #935 landed minutes later and re-added its own children()
and __contains__ without seeing #934's, so the second definitions silently
shadowed the first: children() returned raw containers and __contains__ resolved
via getattr (which fires @Property descriptors). That broke
test_module_children_preserves_direct_child_tree.

Remove the duplicate definitions and keep #934's versions. The full MLX suite,
including the output-head resolution paths #935 targeted, stays green.

Co-authored-by: danielhanchen <unslothai@gmail.com>

Author: danielhanchen

tests/mlx_simulation/mlx_nn_stub.py

@@ -143,32 +143,6 @@ def named_modules(self, prefix=""):
                         sub_prefix = f"{prefix}.{attr_name}.{k}" if prefix else f"{attr_name}.{k}"
                         yield from item.named_modules(sub_prefix)
 
-    def __contains__(self, key):
-        """MLX's Module derives from dict, so ``"bias" in module`` is valid on
-        any module and checks the parameter/child entry. Mirror that here by
-        answering for tensor- or Module-valued attributes; subclasses whose
-        parameters live on a wrapped torch module (Linear) override this."""
-        value = getattr(self, key, None)
-        return isinstance(value, (torch.Tensor, Module))
-
-    def children(self):
-        """Direct sub-structure keyed by attribute name, mirroring MLX's
-        ``Module.children()``: Module-valued attributes map to the Module,
-        list/dict containers of Modules map to the container itself (MLX
-        returns the nested structure; consumers type-check the values, so
-        containers fall through their exact-type filters unchanged)."""
-        out = {}
-        for attr_name, attr_val in vars(self).items():
-            if isinstance(attr_val, Module):
-                out[attr_name] = attr_val
-            elif isinstance(attr_val, (list, tuple)):
-                if any(isinstance(item, Module) for item in attr_val):
-                    out[attr_name] = attr_val
-            elif isinstance(attr_val, dict):
-                if any(isinstance(item, Module) for item in attr_val.values()):
-                    out[attr_name] = attr_val
-        return out
-
     def freeze(self, *, recurse=True, keys=None):
         return self