code: def _fit(self, dataset: Dataset) -> Preprocessor:
      self.stats_ = dataset.aggregate(Max("id"))
  
imports: import pandas
  import ray
  from ray.data.preprocessors import MinMaxScaler
  from ray.data.preprocessors.scaler import StandardScaler
  import ray
  from ray.data.preprocessors import MinMaxScaler
  from ray.train.xgboost import XGBoostTrainer
  from ray.train import ScalingConfig
  import ray
  from ray.data.preprocessors import MinMaxScaler, SimpleImputer
  from typing import Dict
  import ray
  from pandas import DataFrame
  from ray.data.preprocessor import Preprocessor
  from ray.data import Dataset
  from ray.data.aggregate import Max
  from ray.data.preprocessors import SimpleImputer
  from ray.data.preprocessors import Concatenator, StandardScaler
label_desc: Use image node_id 1 for calling the CustomPreprocessor obj's underlying member method code with example usage: obj._fit(dataset) without return types