Avoid attempting variable equality checks implied by python in.

PiperOrigin-RevId: 590992962

tf_keras/optimizers/optimizer.py

@@ -580,7 +580,13 @@ def _trackable_children(self, save_type="checkpoint", **kwargs):
  for var in val:
  if hasattr(var, "_sharded_container"):
  sv = var._sharded_container()
- if sv not in sv_vals:
+ # Use unique id to check existence. `in` would
+ # attempt element-wise variable value
+ # comparison.
+ if not any(
+ sv._unique_id == other_sv._unique_id
+ for other_sv in sv_vals
+ ):
  sv_vals.append(sv)
  else:
  sv_vals.append(var)