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# Add support for W&B hyperparameter sweep
This PR:
* allows using wandb for running hyperparameter search.
* The runs are visualized on W&B sweeps dashboard
* This supports runnning sweeps on parallel devices, all reporting to the same central dashboard.

### Usage
**To run new a hyperparameter search:**
```
trainer.hyperparameter_search(
    backend="wandb", 
    project="transformers_sweep", # name of the project
    n_trials=5,
    metric="eval/loss", # metric to be optimized, default 'eval/loss'. A warning is raised if the passed metric is not found
)
```
This outputs a sweep id. Eg. `my_project/sweep_id`

**To run sweeps on parallel devices:**
Just pass sweep id which you want to run parallel
```
trainer.hyperparameter_search(
    backend="wandb", 
    sweep_id = "my_project/sweep_id"
)
```