The xgb.get_booster().get_dump() shows that some of individual trees are empty (no variable printed - only constants).

```
['0:leaf=-0.0190534852\n',
'0:leaf=-0.0190102123\n',
'0:leaf=-0.0187628437\n',
'0:leaf=-0.0185498875\n',
'0:[sump_any_any_any_any_any<196911]
yes=1,no=2,missing=1\n\t1:leaf=-0.0185494889\n\t2:leaf=-0.0176288597\n',
'0:[sumd_per_any_any_any_trg<2115.5]
yes=1,no=2,missing=1\n\t1:leaf=-0.0183512494\n\t2:leaf=-0.0171739999\n',
'0:leaf=-0.0180586521\n',
'0:[sumd_per_any_any_any_trg<2908]
yes=1,no=2,missing=1\n\t1:leaf=-0.0179917756\n\t2:leaf=-0.0167234316\n',
```