code: def split_fn(df):
      return [([0, 1], [[2, 3], [2], [3]]), ([2, 3], [[0, 1]])], [
          {"fold": 1},
          {"fold": 2},
      ]
  
file_path: fklearn/tests/validation/test_validator.py
imports: import warnings
  from datetime import datetime, timedelta
  import pandas
  from toolz.functoolz import identity
  from fklearn.training.classification import lgbm_classification_learner
  from fklearn.validation import splitters, evaluators
  from fklearn.validation.validator import validator_iteration, validator, parallel_validator
  from fklearn.validation.perturbators import perturbator, nullify
  import pytest
label_desc: Use image node_id 3 for calling a global function with example usage: split_fn(df) and returns: list,  list