code: def choice(self, candidates, mutator, model, index):
      idx = (self.iteration + index) % len(candidates)
      return candidates[idx]
  
imports: import json
  from pathlib import Path
  import pytest
  from nni.common.framework import get_default_framework, set_default_framework
  from nni.nas.space import StationaryMutator, Mutator, MutationSampler, GraphModelSpace, ModelStatus, MutatorSequence
  from nni.nas.space.mutator import _RandomSampler
  from nni.nas.space.graph_op import Operation
label_desc: Use image node_id 2 for calling the DebugSampler obj's underlying member method code with example usage: obj.choice(candidates, mutator, model, index) and returns: candidates