code: def test_string(self):
      for dtype in ("tensor", "numpy"):
          # string input
          result = EnsureType(data_type=dtype)("test_string")
          self.assertTrue(isinstance(result, str))
          self.assertEqual(result, "test_string")
          # numpy array of string
          result = EnsureType(data_type=dtype)(
              np.array(["test_string0", "test_string1"])
          )
          self.assertTrue(isinstance(result, np.ndarray))
          self.assertEqual(result[1], "test_string1")
  
file_path: MONAI/tests/test_ensure_type.py
imports: from __future__ import annotations
  import unittest
  import numpy
  import torch
  from monai.data import MetaTensor
  from monai.transforms import EnsureType
  from tests.utils import assert_allclose
label_desc: Use image node_id 3 for calling the TestEnsureType obj's underlying member method code with example usage: obj.test_string() without return types