How to understand Xgboost model dump

Question

Noticed that spark xgboost does not have a API trees_to_dataframe() as that in Python API, I am trying to parse the getModelDump result, but I am confused on its format, which fields represents what etc.

 // train xgb_model in spark version of xgboost
scala> xgb_model
res18: ml.dmlc.xgboost4j.scala.spark.XGBoostClassificationModel = xgbc_89286dd04aa3

scala> xgb_model.nativeBooster.getModelDump(null, true);
res19: Array[String] =
Array("0:[f1<53] yes=1,no=2,missing=2,gain=58047.7812,cover=336165
        1:[f3<53.9500008] yes=3,no=4,missing=3,gain=24677.3848,cover=63748.25
                3:leaf=-0.0531237721,cover=53626.5
                4:leaf=0.031994272,cover=10121.75
        2:[f16<1.66669905] yes=5,no=6,missing=6,gain=10181.9785,cover=272416.75
                5:leaf=-0.0937986076,cover=268367
                6:leaf=-0.0139159411,cover=4049.75
", "0:[f1<51] yes=1,no=2,missing=2,gain=52816.4062,cover=336097.594
        1:[f8<369.570007] yes=3,no=4,missing=4,gain=22681.3555,cover=60529.668
                3:leaf=-0.0121749714,cover=37363.5625
                4:leaf=-0.0751453713,cover=23166.1055
        2:[f16<1.67979908] yes=5,no=6,missing=6,gain=10274.8359,cover=275567.906
                5:leaf=-0.089068912,cover=271300.188
                6:leaf=-0.0108754979,cover=4267.74268
", "0:[f1<56] yes=1,no=2,missing=2,gain=4887...

scala> res19.size
res20: Int = 200

My Model parameter settings is below :

xgbParams = {'n_estimators': 200, 'max_depth': 2, 'eta': 0.05, 'lambda':1, 'gamma':4, 'alpha':0.1, 'subsample':0.8, #'min_child_weight': 1,
         'colsample_bytree':0.8, 'objective': 'binary:logistic', 'colsample_bylevel':0.8,
         'eval_metric':'logloss', 'seed': 1122, 'missing': -999999999}

I think the res19.size = 200 makes sens, as I have set n_estimators to 200. I am confused on each string in res19, which all formatted as below: I think f2 must represent some certain feature, but how can I find the examply feature name ? Also, what does 0, 1, 2 represent? and what does yes=3, no=4 mean ?

I have also checked understanding-python-xgboost-model-dump-output-of-a-very-simple-tree but that posts only explain the value represented by the leaf node.

Thanks in advance !!

0:[f2<0.380098999] yes=1,no=2,missing=1,gain=732.850342,cover=72529.7266
        1:[f47<31.9999981] yes=3,no=4,missing=3,gain=753.887451,cover=67352.3594
                3:leaf=4.21585646e-05,cover=63820.7422
                4:leaf=0.0237709191,cover=3531.61987
        2:[f4<1050] yes=5,no=6,missing=6,gain=410.277802,cover=5177.3667
                5:leaf=0.00518732425,cover=1373.32422
                6:leaf=-0.0266880095,cover=3804.04224

```