class_docstr: Handles :meth:`Mutator.choice` calls.
  
  Choice is the only supported type for mutator.
class_docstr_tok: ["Handles",":","meth",":","`","Mutator.choice","`","calls",".","Choice","is","the","only","supported","type","for","mutator","."]
code: def choice(
      self,
      candidates: List[Choice],
      mutator: "Mutator",
      model: GraphModelSpace,
      index: int,
  ) -> Choice:
      raise NotImplementedError()
  
imports: from __future__ import annotations
  from contextlib import contextmanager
  from typing import Any, Callable, Iterable, List, Optional, TYPE_CHECKING, Iterator
  from numpy.random import RandomState
  from nni.mutable import LabeledMutable, MutableList, MutableDict, Categorical, Mutable, SampleValidationError, Sample, SampleMissingError, label_scope, auto_label, frozen_context
  from .space import ModelStatus
label_desc: Use image node_id 1 for calling the MutationSampler obj's underlying member method code with example usage: obj.choice(candidates, mutator, model, index) without return types