code: def testHStack(self):
      with self.session():
          p1 = array_ops.placeholder(dtypes.float32, shape=[4, 4])
          p2 = array_ops.placeholder(dtypes.float32, shape=[4, 4])
          c = array_ops.concat([p1, p2], 0)
          params = {
              p1: np.random.rand(4, 4).astype("f"),
              p2: np.random.rand(4, 4).astype("f"),
          }
          result = c.eval(feed_dict=params)
  
      self.assertEqual(result.shape, c.get_shape())
      self.assertAllEqual(result[:4, :], params[p1])
      self.assertAllEqual(result[4:, :], params[p2])
  
imports: import numpy
  from tensorflow.python.eager import def_function
  from tensorflow.python.framework import constant_op
  from tensorflow.python.framework import dtypes
  from tensorflow.python.framework import errors_impl
  from tensorflow.python.framework import ops
  from tensorflow.python.framework import test_util
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import gen_array_ops
  from tensorflow.python.ops import gradient_checker
  from tensorflow.python.ops import gradients_impl
  from tensorflow.python.ops import math_ops
  from tensorflow.python.ops import nn_ops
  from tensorflow.python.ops import variables
  from tensorflow.python.platform import test
label_desc: Use image node_id 1 for calling the ConcatOpTest obj's underlying member method code with example usage: obj.testHStack() without return types