code: def setup_class(cls):
      from sklearn.datasets import load_breast_cancer
  
      X, y = load_breast_cancer(return_X_y=True)
      cls.X = X
      cls.y = y
  
      split = int(X.shape[0] * 0.8)
      cls.X_train = X[:split, ...]
      cls.y_train = y[:split, ...]
      cls.X_valid = X[split:, ...]
      cls.y_valid = y[split:, ...]
  
imports: import json
  import os
  import tempfile
  from typing import Union
  import pytest
  import xgboost
  from xgboost import testing
label_desc: Use image node_id 1 for calling the TestCallbacks obj's underlying member method code with example usage: obj.setup_class(cls) without return types