Add zh_dureader_model_v2 && add train function

[sfwydyc]

Add zh_dureader_model_v2 && add train function

[CLAassistant]

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0 out of 3 committers have signed the CLA.

❌ sfwydyc
❌ MrTuo
❌ procedure2012

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[procedure2012]

Everything is alright.