message: Add blank_index parameter at ctc_greedy_decoder in ctc_ops
  If blank_index is None then num_classes - 1
diff: @@ -284,7 +284,10 @@ def _CTCLossV2Grad(op, grad_loss, _):
  @tf_export("nn.ctc_greedy_decoder")
  -def ctc_greedy_decoder(inputs, sequence_length, merge_repeated=True):
  +def ctc_greedy_decoder(inputs,
  + sequence_length,
  + merge_repeated=True,
  + blank_index=None):
  """Performs greedy decoding on the logits given in input (best path).
  Note: Regardless of the value of merge_repeated, if the maximum index of a
  @@ -325,8 +328,12 @@ def ctc_greedy_decoder(inputs, sequence_length, merge_repeated=True):
  sequence found, the negative of the sum of the greatest logit at each
  timeframe.
  """
  +
  + if blank_index is None:
  + blank_index = _get_dim(inputs, 2)
  +
  outputs = gen_ctc_ops.ctc_greedy_decoder(
  - inputs, sequence_length, merge_repeated=merge_repeated)
  + inputs, sequence_length, merge_repeated=merge_repeated, blank_index=blank_index)
  (decoded_ix, decoded_val, decoded_shape, log_probabilities) = outputs
  return ([sparse_tensor.SparseTensor(decoded_ix, decoded_val,
  decoded_shape)], log_probabilities)
  