[bugs] 1. fix chinese_ref column will ignore even we add it in to Datasets.
Author: johnson7788
Pull request: yes

[bugs] 1. fix chinese_ref column will ignore even we add it in to Datasets.
[bugs] 2. DataCollatorForWholeWordMask e["chinese_ref"] is a list, fix the get length method.

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Fixes # (issue)
I follow the examples/language-modeling/run_mlm_wwm.py, chinese whole word mask, found chinese_ref column not used even i add it into datasets, and because it has been removed by trainer.py function  _remove_unused_columns()

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Comments:
You can avoid removing that column by setting `remove_unused_columns=False` in your `TrainingArguments`.

I will try it,thank you so much