Flashlight and Pyctcdecode decoders
This PR is stale because it has been open for 14 days with no activity. Remove stale label or comment or update or this will be closed in 7 days. This PR was closed because it has been inactive for 7 days since being marked as stale. @karpnv is this being worked on ? @karpnv i'll provide a review later this week (bandwidth limited) @titu1994 I covered half of [the table](https://docs.google.com/spreadsheets/d/11feRNo9Bx0jnS947PkeGd0j8wPOgw4CIVfRnzpqZe48/edit?usp=sharing) and PR already huge. let's review it first. Then will continue with AggregateTokenizer Jenkins Note: `eval_beamsearch_ngram_ctc.py` and transducer.py I guess also requires changes for hypothesis that was updated recently for log probs.  This PR is stale because it has been open for 14 days with no activity. Remove stale label or comment or update or this will be closed in 7 days. This PR was closed because it has been inactive for 7 days since being marked as stale. This PR is stale because it has been open for 14 days with no activity. Remove stale label or comment or update or this will be closed in 7 days. This PR was closed because it has been inactive for 7 days since being marked as stale. [🤖]: Hi @karpnv 👋,

I just wanted to let you know that, you know, a [CICD pipeline](https://github.com/NVIDIA/NeMo/actions/runs/11126811833) for this PR just finished successfully ✨

So it might be time to merge this PR or like to get some approvals 🚀

But I'm just a 🤖 so I'll leave it you what to do next.

Have a great day! 

//cc @ko3n1g This PR is stale because it has been open for 14 days with no activity. Remove stale label or comment or update or this will be closed in 7 days. can we merge this?  This PR is stale because it has been open for 14 days with no activity. Remove stale label or comment or update or this will be closed in 7 days. @karpnv could you fix merge conflicts so this can be merged? This PR is stale because it has been open for 14 days with no activity. Remove stale label or comment or update or this will be closed in 7 days. @karpnv is this going to be completed or should we close it? This PR is stale because it has been open for 14 days with no activity. Remove stale label or comment or update or this will be closed in 7 days. This PR is stale because it has been open for 14 days with no activity. Remove stale label or comment or update or this will be closed in 7 days. <!-- pylint-output-strict-mode-false -->

beep boop 🤖: 🙏 The following files have warnings. In case you are familiar with these, please try helping us to improve the code base.

---

Your code was analyzed with PyLint. The following annotations have been identified:

```
************* Module speech_to_text_eval
examples/asr/speech_to_text_eval.py:86:0: C0115: Missing class docstring (missing-class-docstring)
examples/asr/speech_to_text_eval.py:113:0: C0116: Missing function or method docstring (missing-function-docstring)
************* Module transcribe_speech
examples/asr/transcribe_speech.py:174:0: C0301: Line too long (139/119) (line-too-long)
examples/asr/transcribe_speech.py:382:0: C0301: Line too long (134/119) (line-too-long)
examples/asr/transcribe_speech.py:111:0: C0115: Missing class docstring (missing-class-docstring)
examples/asr/transcribe_speech.py:118:0: C0115: Missing class docstring (missing-class-docstring)
examples/asr/transcribe_speech.py:210:0: C0116: Missing function or method docstring (missing-function-docstring)
examples/asr/transcribe_speech.py:15:0: W0611: Unused import contextlib (unused-import)
************* Module nemo.collections.asr.models.hybrid_rnnt_ctc_models
nemo/collections/asr/models/hybrid_rnnt_ctc_models.py:123:0: C0301: Line too long (266/119) (line-too-long)
nemo/collections/asr/models/hybrid_rnnt_ctc_models.py:224:0: C0301: Line too long (120/119) (line-too-long)
nemo/collections/asr/models/hybrid_rnnt_ctc_models.py:674:0: C0301: Line too long (141/119) (line-too-long)
nemo/collections/asr/models/hybrid_rnnt_ctc_models.py:675:0: C0301: Line too long (139/119) (line-too-long)
nemo/collections/asr/models/hybrid_rnnt_ctc_models.py:16:0: W0611: Unused import json (unused-import)
nemo/collections/asr/models/hybrid_rnnt_ctc_models.py:17:0: W0611: Unused import os (unused-import)
nemo/collections/asr/models/hybrid_rnnt_ctc_models.py:18:0: W0611: Unused import tempfile (unused-import)
nemo/collections/asr/models/hybrid_rnnt_ctc_models.py:24:0: W0611: Unused tqdm imported from tqdm.auto (unused-import)
************* Module nemo.collections.asr.modules.flashlight_decoder
nemo/collections/asr/modules/flashlight_decoder.py:49:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/modules/flashlight_decoder.py:53:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/modules/flashlight_decoder.py:57:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/modules/flashlight_decoder.py:61:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/modules/flashlight_decoder.py:65:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/modules/flashlight_decoder.py:76:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/modules/flashlight_decoder.py:83:0: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/modules/flashlight_decoder.py:292:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/modules/flashlight_decoder.py:17:0: W0611: Unused Iterable imported from typing (unused-import)
nemo/collections/asr/modules/flashlight_decoder.py:17:0: W0611: Unused Tuple imported from typing (unused-import)
nemo/collections/asr/modules/flashlight_decoder.py:23:0: W0611: Unused typecheck imported from nemo.core.classes (unused-import)
nemo/collections/asr/modules/flashlight_decoder.py:24:0: W0611: Unused LengthsType imported from nemo.core.neural_types (unused-import)
nemo/collections/asr/modules/flashlight_decoder.py:24:0: W0611: Unused LogprobsType imported from nemo.core.neural_types (unused-import)
nemo/collections/asr/modules/flashlight_decoder.py:24:0: W0611: Unused NeuralType imported from nemo.core.neural_types (unused-import)
nemo/collections/asr/modules/flashlight_decoder.py:24:0: W0611: Unused PredictionsType imported from nemo.core.neural_types (unused-import)
************* Module nemo.collections.asr.parts.submodules.ctc_beam_decoding
nemo/collections/asr/parts/submodules/ctc_beam_decoding.py:197:0: C0301: Line too long (123/119) (line-too-long)
nemo/collections/asr/parts/submodules/ctc_beam_decoding.py:38:0: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/parts/submodules/ctc_beam_decoding.py:62:0: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/parts/submodules/ctc_beam_decoding.py:210:0: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/parts/submodules/ctc_beam_decoding.py:898:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/asr/parts/submodules/ctc_beam_decoding.py:910:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/asr/parts/submodules/ctc_beam_decoding.py:920:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/asr/parts/submodules/ctc_beam_decoding.py:937:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/asr/parts/submodules/ctc_beam_decoding.py:944:0: C0115: Missing class docstring (missing-class-docstring)
************* Module nemo.collections.asr.parts.submodules.ctc_decoding
nemo/collections/asr/parts/submodules/ctc_decoding.py:263:0: C0301: Line too long (209/119) (line-too-long)
nemo/collections/asr/parts/submodules/ctc_decoding.py:342:0: C0301: Line too long (136/119) (line-too-long)
nemo/collections/asr/parts/submodules/ctc_decoding.py:736:0: C0301: Line too long (151/119) (line-too-long)
nemo/collections/asr/parts/submodules/ctc_decoding.py:893:0: C0301: Line too long (125/119) (line-too-long)
nemo/collections/asr/parts/submodules/ctc_decoding.py:33:0: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/parts/submodules/ctc_decoding.py:967:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/parts/submodules/ctc_decoding.py:978:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/parts/submodules/ctc_decoding.py:989:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/parts/submodules/ctc_decoding.py:1449:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/asr/parts/submodules/ctc_decoding.py:1496:0: C0115: Missing class docstring (missing-class-docstring)
************* Module scripts.asr_language_modeling.ngram_lm.create_lexicon_from_arpa
scripts/asr_language_modeling/ngram_lm/create_lexicon_from_arpa.py:33:0: C0116: Missing function or method docstring (missing-function-docstring)
************* Module scripts.asr_language_modeling.ngram_lm.eval_beamsearch_ngram_ctc
scripts/asr_language_modeling/ngram_lm/eval_beamsearch_ngram_ctc.py:19:0: C0301: Line too long (125/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/eval_beamsearch_ngram_ctc.py:54:0: C0301: Line too long (141/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/eval_beamsearch_ngram_ctc.py:55:0: C0301: Line too long (160/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/eval_beamsearch_ngram_ctc.py:175:0: C0301: Line too long (121/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/eval_beamsearch_ngram_ctc.py:205:0: C0301: Line too long (125/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/eval_beamsearch_ngram_ctc.py:284:0: C0301: Line too long (120/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/eval_beamsearch_ngram_ctc.py:371:0: C0301: Line too long (122/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/eval_beamsearch_ngram_ctc.py:372:0: C0301: Line too long (148/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/eval_beamsearch_ngram_ctc.py:422:0: C0301: Line too long (138/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/eval_beamsearch_ngram_ctc.py:424:0: C0301: Line too long (157/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/eval_beamsearch_ngram_ctc.py:135:0: C0116: Missing function or method docstring (missing-function-docstring)
scripts/asr_language_modeling/ngram_lm/eval_beamsearch_ngram_ctc.py:283:0: C0116: Missing function or method docstring (missing-function-docstring)
************* Module scripts.asr_language_modeling.ngram_lm.eval_beamsearch_ngram_transducer
scripts/asr_language_modeling/ngram_lm/eval_beamsearch_ngram_transducer.py:18:0: C0301: Line too long (129/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/eval_beamsearch_ngram_transducer.py:108:0: C0301: Line too long (126/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/eval_beamsearch_ngram_transducer.py:109:0: C0301: Line too long (140/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/eval_beamsearch_ngram_transducer.py:111:0: C0301: Line too long (149/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/eval_beamsearch_ngram_transducer.py:112:0: C0301: Line too long (162/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/eval_beamsearch_ngram_transducer.py:118:0: C0301: Line too long (139/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/eval_beamsearch_ngram_transducer.py:164:0: C0301: Line too long (245/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/eval_beamsearch_ngram_transducer.py:225:0: C0301: Line too long (149/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/eval_beamsearch_ngram_transducer.py:229:0: C0301: Line too long (132/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/eval_beamsearch_ngram_transducer.py:232:0: C0301: Line too long (124/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/eval_beamsearch_ngram_transducer.py:384:0: C0301: Line too long (121/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/eval_beamsearch_ngram_transducer.py:124:0: C0116: Missing function or method docstring (missing-function-docstring)
scripts/asr_language_modeling/ngram_lm/eval_beamsearch_ngram_transducer.py:240:0: C0116: Missing function or method docstring (missing-function-docstring)
************* Module scripts.asr_language_modeling.ngram_lm.kenlm_utils
scripts/asr_language_modeling/ngram_lm/kenlm_utils.py:20:0: C0301: Line too long (129/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/kenlm_utils.py:21:0: C0301: Line too long (124/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/kenlm_utils.py:80:0: C0301: Line too long (129/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/kenlm_utils.py:53:0: C0116: Missing function or method docstring (missing-function-docstring)
scripts/asr_language_modeling/ngram_lm/kenlm_utils.py:58:0: C0116: Missing function or method docstring (missing-function-docstring)
scripts/asr_language_modeling/ngram_lm/kenlm_utils.py:104:0: C0116: Missing function or method docstring (missing-function-docstring)
scripts/asr_language_modeling/ngram_lm/kenlm_utils.py:130:0: C0116: Missing function or method docstring (missing-function-docstring)
scripts/asr_language_modeling/ngram_lm/kenlm_utils.py:180:0: C0116: Missing function or method docstring (missing-function-docstring)
scripts/asr_language_modeling/ngram_lm/kenlm_utils.py:189:0: C0116: Missing function or method docstring (missing-function-docstring)
scripts/asr_language_modeling/ngram_lm/kenlm_utils.py:216:0: C0116: Missing function or method docstring (missing-function-docstring)
scripts/asr_language_modeling/ngram_lm/kenlm_utils.py:230:0: C0116: Missing function or method docstring (missing-function-docstring)
scripts/asr_language_modeling/ngram_lm/kenlm_utils.py:240:0: C0116: Missing function or method docstring (missing-function-docstring)
************* Module scripts.asr_language_modeling.ngram_lm.ngram_merge
scripts/asr_language_modeling/ngram_lm/ngram_merge.py:65:0: C0301: Line too long (122/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/ngram_merge.py:111:0: C0301: Line too long (395/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/ngram_merge.py:115:0: C0301: Line too long (201/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/ngram_merge.py:117:0: C0301: Line too long (161/119) (line-too-long)
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scripts/asr_language_modeling/ngram_lm/ngram_merge.py:250:0: C0301: Line too long (156/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/ngram_merge.py:274:0: C0301: Line too long (147/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/ngram_merge.py:437:0: C0301: Line too long (140/119) (line-too-long)
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scripts/asr_language_modeling/ngram_lm/ngram_merge.py:473:0: C0301: Line too long (129/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/ngram_merge.py:59:0: C0115: Missing class docstring (missing-class-docstring)
************* Module scripts.asr_language_modeling.ngram_lm.train_kenlm
scripts/asr_language_modeling/ngram_lm/train_kenlm.py:63:0: C0301: Line too long (133/119) (line-too-long)
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scripts/asr_language_modeling/ngram_lm/train_kenlm.py:81:0: C0301: Line too long (128/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/train_kenlm.py:87:0: C0116: Missing function or method docstring (missing-function-docstring)

-----------------------------------
Your code has been rated at 9.57/10
```

---

Mitigation guide:

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Thank you for improving NeMo's documentation! This PR is stale because it has been open for 14 days with no activity. Remove stale label or comment or update or this will be closed in 7 days. This PR was closed because it has been inactive for 7 days since being marked as stale.
# Preserve Flashlight and Pyctcdecode beamsearch with Ngram LM 

Support Flashlight and Pyctcdecode decoding with pure KenLM and NeMo KenLM 
Standardize API of CLI inference scripts

**Collection**: ASR

# Changelog 
- Fix install script install_beamsearch_decoders.sh
- Create flashlight_lexicon file during scripts/asr_language_modeling/ngram_lm/train_kenlm.py and tar it with kenlm.bin
- Unify parameters for eval_beamsearch_ngram_ctc.py, speech_to_text_eval.py and training
-- Get logprobs from Hypothesis
-- Use "pyctcdecode" strategy as default beamsearch algorithm denoted as "beam"
-- Remove default seq2seq strategy
-- Check decoding_type and search_type combinations
-- Support empty string in nemo_kenlm_path and word_kenlm_path  for beamsearch without LM (ZeroLM)
- Fix bug with EncDecHybridRNNTCTCModel in examples/asr/transcribe_speech.py 
- Support AggregateTokenizer in scripts/asr_language_modeling/ngram_lm/create_lexicon_from_arpa.py

```python
python3 scripts/asr_language_modeling/ngram_lm/eval_beamsearch_ngram_ctc.py \
model_path=am_model.nemo  \
dataset_manifest=manifest.json  \
preds_output_folder=/tmp   \
ctc_decoding.strategy=flashlight \
ctc_decoding.beam.kenlm_path=am_model.kenlm \
ctc_decoding.beam.beam_size=[4]   \
ctc_decoding.beam.beam_alpha=[0.5]   \
ctc_decoding.beam.beam_beta=[0.5] \
batch_size=32  \
beam_batch_size=1 \
cuda=1

python3 examples/asr/speech_to_text_eval.py  \
model_path=am_model.nemo \ 
dataset_manifest=manifest.json \
decoder_type=ctc  
ctc_decoding.strategy=flashlight \  
ctc_decoding.beam.nemo_kenlm_path=kenlm_model.bin \
ctc_decoding.beam.beam_size=4   \
ctc_decoding.beam.beam_alpha=0.5   \
ctc_decoding.beam.beam_beta=0.5 \
ctc_decoding.beam.flashlight_cfg.lexicon_path=am_model.flashlight_lexicon \ # DEFAULT_TOKEN_OFFSET
ctc_decoding.beam.return_best_hypothesis=true \
batch_size=32  \
output_filename=/tmp/manifest_out.json 
cuda=1
```
**PR Type**:
- [ V] New Feature
- [ ] Bugfix
- [ ] Documentation

If you haven't finished some of the above items you can still open "Draft" PR.


## Who can review?


# Additional Information
* Related to #9067
