No lambda, gamma for XGBoostRegressionTree?

[jinwoolim8180]

I am new to XGBoost and I was trying to study it through your code.
I found that lambda and gamma(min_split_loss) were missing and these values should be considered in function _gain_by_taylor and _approximate_update.
Also I think some of the important features such as pruning are missing in your code... Didn't look at the code thoroughly so I could be wrong