code: def testRankOne(self):
      input_array = ["this", "is", "a", "test"]
      truth = "thisisatest"
      truth_shape = []
      self._testReduceJoin(input_array, truth, truth_shape, axis=0)
  
imports: import itertools
  import numpy
  from tensorflow.python.framework import constant_op
  from tensorflow.python.framework import dtypes
  from tensorflow.python.framework import test_util
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import string_ops
  from tensorflow.python.platform import test
label_desc: Use image node_id 3 for calling the ReduceJoinTest obj's underlying member method code with example usage: obj.testRankOne() without return types