get_linear_schedule_with_warmup method can't be found in optimization.py
# 🐛 Bug

## Information

Model I am using (Bert, XLNet ...): BERT

Language I am using the model on (English, Chinese ...): English

The problem arises when using:
* [ ] the official example scripts: (give details below)
* [ ] my own modified scripts: (give details below)

My transformer was downloaded from anaconda cloud by using command "conda install -c conda-forge transformers", when I tried to use AdamW as what you show in the example, I found there is no **get_linear_schedule_with_warmup** in the **transformers.optimization.py** file for me to create a scheduler.

The tasks I am working on is:
* [ ] an official GLUE/SQUaD task: (give the name)
* [ ] my own task or dataset: (give details below)

## To reproduce

Steps to reproduce the behavior:

1.
2.
3.

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## Expected behavior

<!-- A clear and concise description of what you would expect to happen. -->

## Environment

* OS:
* Python version:
* PyTorch version:
* `transformers` version (or branch):
* Using GPU ?
* Distributed or parallel setup ?
* Any other relevant information:

There clearly is:

https://github.com/huggingface/transformers/blob/0aa40e9569a71306036de3a217eed55521699604/src/transformers/optimization.py#L47-L59

Please fill out the complete template - it's there for a reason. If you had shown us which version you're working with, we could probably tell you that your version is too late, or at least dig further. Now we can't help at all, it's just guess work.

Give code, full error trace, and your PyTorch/Tensorflow version.<|||||>I thought my transformers was the lastest version, but I found it's not when I checked it on the anaconda cloud "https://anaconda.org/conda-forge/transformers". The problem has been solved after reinstalling, Thanks for your reply :)<|||||>In the future, please fill out the complete template. Please close this question if you don't have any more questions.<|||||>OK