code: def testStringJoin(self):
      input0 = ["a", "b"]
      input1 = "a"
      input2 = [["b"], ["c"]]
  
      output = string_ops.string_join([input0, input1])
      self.assertAllEqual(output, [b"aa", b"ba"])
  
      output = string_ops.string_join([input0, input1], separator="--")
      self.assertAllEqual(output, [b"a--a", b"b--a"])
  
      output = string_ops.string_join(
          [input0, input1, input0], separator="--"
      )
      self.assertAllEqual(output, [b"a--a--a", b"b--a--b"])
  
      output = string_ops.string_join([input1] * 4, separator="!")
      self.assertEqual(self.evaluate(output), b"a!a!a!a")
  
      output = string_ops.string_join([input2] * 2, separator="")
      self.assertAllEqual(output, [[b"bb"], [b"cc"]])
  
      output = string_ops.string_join([])
      self.assertAllEqual(output, b"")
  
      with self.assertRaisesRegex(
          (ValueError, errors.InvalidArgumentError),
          "shapes do not match|must be equal rank",
      ):
          self.evaluate(string_ops.string_join([input0, input2]))
  
imports: from tensorflow.python.framework import errors
  from tensorflow.python.ops import string_ops
  from tensorflow.python.platform import test
label_desc: Use image node_id 1 for calling the StringJoinOpTest obj's underlying member method code with example usage: obj.testStringJoin() without return types