code: def test_string_adt():
      s = mxnet.container.String("xyz")
      arr = mxnet._ffi.convert_to_node([s, s])
      assert arr[0] == s
      assert isinstance(arr[0], mxnet.container.String)
  
file_path: mxnet/tests/python/unittest/test_ffi_container.py
imports: import mxnet
  import numpy
  from mxnet import np, npx, _api_internal
  from mxnet.ndarray import NDArray
  from mxnet.test_utils import use_np
label_desc: Use image node_id 3 for calling a global function with example usage: test_string_adt() without return types