message: Replace set, dict with ObjectIdentityDict/Set to prepare for eq implementation
diff: @@ -153,7 +153,7 @@ def _lift_unlifted_variables(graph, variable_holder):
  ops.GraphKeys.LOCAL_VARIABLES)
  existing_captures = object_identity.ObjectIdentitySet(
  graph.internal_captures)
  - lifted_variables = {}
  + lifted_variables = object_identity.ObjectIdentityDictionary()
  def _should_lift_variable(v):
  return ((v._in_graph_mode # pylint: disable=protected-access
  