code: def test_k_val(self, k_val):
      with pytest.raises(ValueError):
          initial_predictions = torch.tensor([0] * 5)
          take_step = take_step_with_timestep
          beam_size = 3
          k_sampler = TopKSampler(k=k_val, with_replacement=True)
  
          top_k, log_probs = BeamSearch(
              self.end_index,
              beam_size=beam_size,
              max_steps=10,
              sampler=k_sampler,
          ).search(initial_predictions, {}, take_step)
  
imports: from typing import Dict, Tuple, Union
  import numpy
  import pytest
  import torch
  from allennlp.common.checks import ConfigurationError
  from allennlp.common.testing import AllenNlpTestCase
  from allennlp.nn.beam_search import MultinomialSampler, BeamSearch, TopKSampler, TopPSampler, GumbelSampler, LengthNormalizedSequenceLogProbabilityScorer, RepeatedNGramBlockingConstraint, StepFunctionTypeWithTimestep, StepFunctionTypeNoTimestep
  from allennlp.common.params import Params
  from allennlp.nn.util import min_value_of_dtype
label_desc: Use image node_id 20 for calling the BeamSearchTest obj's underlying member method code with example usage: obj.test_k_val(k_val) without return types