# Hugging Face Transformers v3.0.0 — Release & Upgrade Intelligence
- **Product:** Hugging Face Transformers (https://huggingface.co)
- **Version:** v3.0.0
- **Released:** Jun 29, 2020
- **Impact Score:** 7/10
- **Breaking Changes:** Source flagged
- **Canonical Analysis:** https://changelogs.us/transformers/updates/v3.0.0/

## Executive Summary (TL;DR)
Hugging Face Transformers v3.0.0. Source highlight: New tokenizer API, TensorFlow improvements, enhanced documentation & tutorials

## Breaking Changes & Deprecations
- Breaking changes since `v2` - In #4874 the language modeling BERT has been split in two: `BertForMaskedLM` and `BertLMHeadModel`. `BertForMaskedLM` therefore cannot do causal language modeling anymore, and cannot accept the `lm_labels` argument.

## New Features
- Directly setting a tokenizer special token attributes (e.g. `tokenizer.mask_token = '<mask>'` now only associate the token to the attribute of the tokenizer but doesn't add the token to the vocabulary if it is not in the vocabulary. Tokens are only added by using the `tokenizer.add_special_tokens()` and `tokenizer.add_tokens()` methods
- A new class `AddedToken` can be used to have a more fine-grained control on how added tokens behave during tokenization. In particular the user can control (1) whether left and right spaces are removed around the token during tokenization (2) whether the token will be identified inside another word and (3) whether the token will be recognized in normalized forms (e.g. in lower case if the tokenizer uses lower-casing)
- Introduced a new enum `TensorType` to map all the possible tensor backends we support: `TensorType.TENSORFLOW`, `TensorType.PYTORCH`, `TensorType.NUMPY`
- Add `pad_to_multiple_of` on tokenizers (reimport) #5054 (@mfuntowicz)
- Added a model summary #4789
- Remove old doc page and add note about cache in installation #5027

## Improvements
- TensorFlow models can now compute the loss themselves, using the `TFPretrainedModel.compute_loss` method. #4530
- Can now resize token embeddings in TensorFlow #4351
- Cleaning TensorFlow models #5229
- Expose classes used in documentation #4808
- Explain how to preview the docs in a PR #4795
- Clean documentation #4849

## Bug Fixes
- Serialization issues where fixed
- [tokenizers] Fix #5081 and improve backward compatibility #5125 (@thomwolf)
- Add more tests on tokenizers serialization - fix bugs #5056 (@thomwolf)
- [Tokenization] Fix #5181 - make #5155 more explicit - move back the default logging level in tests to WARNING #5252 (@thomwolf)
- [tokenizers] Several small improvements and bug fixes #5287
- Fix all sphynx warnings #5068 (@sgugger)

## Upgrade Command
```bash
python -m pip install 'transformers==3.0.0'
```