code: def test_double_wrap_no_op(self):
      class A:
          a: int
  
      self.assertFalse(hasattr(A, "_flax_dataclass"))
  
      A = struct.dataclass(A)
      self.assertTrue(hasattr(A, "_flax_dataclass"))
  
      A = struct.dataclass(A)  # no-op
      self.assertTrue(hasattr(A, "_flax_dataclass"))
  
file_path: flax/tests/struct_test.py
imports: import dataclasses
  from typing import Any
  import jax
  from absl.testing import absltest
  from jax._src.tree_util import prefix_errors
  from flax import struct
label_desc: Use image node_id 5 for calling the StructTest obj's underlying member method code with example usage: obj.test_double_wrap_no_op() without return types