code: def test_string():
      x = mxnet.container.String("xyz")
      assert isinstance(x, mxnet.container.String)
      assert isinstance(x, str)
      assert x.startswith("xy")
      assert x + "1" == "xyz1"
      y = _api_internal._echo(x)
      assert isinstance(y, mxnet.container.String)
      assert x.__mxnet_object__.same_as(y.__mxnet_object__)
      assert x == y
  
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 2 for calling a global function with example usage: test_string() without return types