Jiaming Yuan 298ebe68ac
[Breaking] Remove learning_rates in Python. (#5155)
* Remove `learning_rates`.

It's been deprecated since we have callback.

* Set `before_iteration` of `reset_learning_rate` to False to preserve 
  the initial learning rate, and comply to the term "reset".

Closes #4709.

* Tests for various `tree_method`.
2019-12-24 14:25:48 +08:00
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2018-11-15 13:56:33 +13:00