code: def get_num_trees(booster: lgbm.Booster) -> int:
      return booster.current_iteration()
  
imports: import math
  import lightgbm
  import pandas
  import pytest
  from sklearn.datasets import load_breast_cancer
  from sklearn.model_selection import train_test_split
  import ray
  from ray import tune
  from ray.train import ScalingConfig
  from ray.train.constants import TRAIN_DATASET_KEY
  from ray.train.lightgbm import LightGBMTrainer
label_desc: Use image node_id 3 for calling a global function with example usage: get_num_trees(booster) and returns: booster