code: def test_single_step(self):
      self.beam_search.max_steps = 1
      expected_top_k = np.array([[1], [2], [3]])
      expected_log_probs = np.log(np.array([0.4, 0.3, 0.2]))
      self._check_results(
          expected_top_k=expected_top_k,
          expected_log_probs=expected_log_probs,
      )
  
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 8 for calling the BeamSearchTest obj's underlying member method code with example usage: obj.test_single_step() without return types