code: def fit(self, x, y=None, num_round=5, **kargs):
      x = convert_to_numpy(x)
      y = convert_to_numpy(y) if y is not None else None
      add_data(x, self.value, "fgBoostFitAdd", self.bigdl_type)
      ts = time()
      x, y = convert_to_jtensor(x, y, **kargs)
      te = time()
      logging.info(f"ndarray to jtensor: [{te-ts} s]")
      return callBigDlFunc(
          self.bigdl_type, "fgBoostFitCall", self.value, y, num_round
      )
  
file_path: BigDL/python/ppml/src/bigdl/ppml/fl/algorithms/fgboost_regression.py
imports: from time import time
  from bigdl.dllib.utils.common import JavaValue
  from bigdl.ppml.fl.data_utils import *
  from bigdl.ppml.fl import *
  from bigdl.ppml.fl.fgboost.utils import add_data
  import logging
label_desc: Use image node_id 2 for calling the FGBoostRegression obj's underlying member method code with example usage: obj.fit(x, y, num_round) and returns: callBigDlFunc