code: def test_lowercase_one_string(self):
      txt = [
          " TExt to loWERcase! ",
      ]
      expected = [
          b" text to lowercase! ",
      ]
      self.assertAllEqual(expected, normalize_ops.case_fold_utf8(txt))
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from absl.testing import parameterized
  from tensorflow.python.framework import errors
  from tensorflow.python.framework import test_util
  from tensorflow.python.ops.ragged import ragged_factory_ops
  from tensorflow.python.platform import test
  from tensorflow_text.python.ops import normalize_ops
label_desc: Use image node_id 1 for calling the NormalizeOpsTest obj's underlying member method code with example usage: obj.test_lowercase_one_string() without return types