```glue_convert_examples_to_features``` for sequence labeling tasks
## 🚀 Feature

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I would like a function like ```glue_convert_examples_to_features``` for sequence labelling tasks.

## Motivation

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The motivation is that I need much better flexibility for  sequence labelling tasks. Its not enough to have a final, and decided for me model, for this task. I want just the features (a sequence of features/embeddings I guess).

## Additional context
This can be generalized to any dataset with a specific format.

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duplicate to  2208