message: Update nn_ops.py
  Added check for pooling_ratio
diff: @@ -5334,6 +5334,8 @@ def fractional_max_pool_v2(value,
  [Graham, 2015](https://arxiv.org/abs/1412.6071)
  ([pdf](https://arxiv.org/pdf/1412.6071.pdf))
  """
  + if pooling_ratio < 1.0:
  + raise ValueError("pooling_ratio should be >= 1.0.")
  pooling_ratio = _get_sequence(pooling_ratio, 2, 3, "pooling_ratio")
  if seed == 0:
  