message: Minor bug fix: When constructing a StructSpec from a Struct, do not include private cached variables.
  (This wasn't really hurting anything, but there's no need for the Spec to have copies of these variables.)
diff: @@ -318,6 +318,8 @@ class StructSpec(type_spec.TypeSpec):
  def from_value(cls, value):
  value_fields = value.__dict__
  spec_fields = nest.map_structure(_replace_tensor_with_spec, value_fields)
  + spec_fields.pop('_tf_struct_cached_type_spec', None)
  + spec_fields.pop('_tf_struct_cached_fields', None)
  return _create_object_from_type_and_dict(cls, spec_fields)
  def __setattr__(self, name, value):
  