message: Change `gen_array_ops._concat_v2` to gen_array_ops.concat_v2`
  as `_` is not needed any more.
diff: @@ -612,7 +612,7 @@ class ConcatOpTest(test.TestCase):
  t1 = [[1, 2, 3], [4, 5, 6]]
  t2 = [[7, 8, 9], [10, 11, 12]]
  - c = gen_array_ops._concat_v2([t1, t2],
  + c = gen_array_ops.concat_v2([t1, t2],
  constant_op.constant(1, dtype=dtype))
  self.assertEqual([2, 6], c.get_shape().as_list())
  output = c.eval()
  