code: def test_full_warns_on_fold_1():
      """[Base] FoldIndex: check warns on folds=1 if not raise_on_exception."""
      with np.testing.assert_warns(UserWarning):
          FoldIndex(1, X, raise_on_exception=False)
  
imports: import os
  import subprocess
  import numpy
  from mlens import config
  from mlens.utils import IdTrain
  from mlens.index import FoldIndex, BlendIndex, SubsetIndex, TemporalIndex, ClusteredSubsetIndex, FullIndex
  from mlens.index.base import partition, prune_train
label_desc: Use image node_id 11 for calling a global function with example usage: test_full_warns_on_fold_1() without return types