from tensorflow.python.framework import ops

      check_shape_op = logging_ops.Assert(
          math_ops.less_equal(array_ops.rank(target), 2),
          ["target's shape should be either [batch_size, 1] or [batch_size]"])
      with ops.control_dependencies([check_shape_op]):
        target = array_ops.reshape(
            target, shape=[array_ops.shape(target)[0], 1])
