code: def test_string(self):
      for dtype in ("tensor", "numpy"):
          # string input
          result = EnsureTyped(keys="data", data_type=dtype)(
              {"data": "test_string"}
          )["data"]
          self.assertTrue(isinstance(result, str))
          self.assertEqual(result, "test_string")
          # numpy array of string
          result = EnsureTyped(keys="data", data_type=dtype)(
              {"data": np.array(["test_string"])}
          )["data"]
          self.assertTrue(isinstance(result, np.ndarray))
          self.assertEqual(result[0], "test_string")
  
file_path: MONAI/tests/test_ensure_typed.py
imports: from __future__ import annotations
  import unittest
  import numpy
  import torch
  from monai.data import MetaTensor
  from monai.transforms import EnsureTyped
  from tests.utils import assert_allclose
label_desc: Use image node_id 3 for calling the TestEnsureTyped obj's underlying member method code with example usage: obj.test_string() without return types