code: def prepare_model(self) -> CausalTreeRegressor:
      ctree = CausalTreeRegressor(
          control_name=self.control_name,
          groups_cnt=True,
          random_state=RANDOM_SEED,
      )
      return ctree
  
imports: import multiprocessing
  from abc import abstractmethod
  import pandas
  import pytest
  from sklearn.model_selection import train_test_split
  from causalml.inference.tree import CausalTreeRegressor, CausalRandomForestRegressor
  from causalml.metrics import ape
  from causalml.metrics import qini_score
  from .const import RANDOM_SEED, ERROR_THRESHOLD
label_desc: Use image node_id 1 for calling the TestCausalTreeRegressor obj's underlying member method code with example usage: obj.prepare_model() and returns: ctree