class_docstr: Tests utility functions.
      
docstr: Tests :func:`texar.tf.utils.str_join`
          
docstr_tok: ["Tests",":","func",":","`","texar.tf.utils.str_join","`"]
code: def test_str_join(self):
      """Tests :func:`texar.tf.utils.str_join`"""
      tokens = np.ones([2, 2, 3], dtype="str")
  
      str_ = utils.str_join(tokens)
      np.testing.assert_array_equal(
          str_, np.asarray([["1 1 1", "1 1 1"], ["1 1 1", "1 1 1"]])
      )
      self.assertIsInstance(str_, np.ndarray)
  
      str_ = utils.str_join(tokens.tolist())
      np.testing.assert_array_equal(
          str_, [["1 1 1", "1 1 1"], ["1 1 1", "1 1 1"]]
      )
      self.assertIsInstance(str_, list)
  
      tokens = [[], ["1", "1"]]
      str_ = utils.str_join(tokens)
      np.testing.assert_array_equal(str_, ["", "1 1"])
  
file_path: texar/tests/utils/utils_test.py
imports: import tempfile
  import numpy
  import tensorflow
  from texar.tf.utils import utils
  from texar.tf.data.vocabulary import Vocab
label_desc: Use image node_id 6 for calling the UtilsTest obj's underlying member method code with example usage: obj.test_str_join() without return types