code: def testUnknownShape(self):
      input_array = [["a"], ["b"]]
      truth = ["ab"]
      truth_shape = None
      with self.cached_session():
          placeholder = array_ops.placeholder(
              dtypes.string, name="placeholder"
          )
          reduced = string_ops.reduce_join(placeholder, axis=0)
          output_array = reduced.eval(
              feed_dict={placeholder.name: input_array}
          )
          self.assertAllEqualUnicode(truth, output_array)
          self.assertAllEqual(truth_shape, reduced.get_shape())
  
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 9 for calling the ReduceJoinTest obj's underlying member method code with example usage: obj.testUnknownShape() without return types