code: def test_prob_t_a_given_s(self):
      # arrange
      src_sentence = ["ich", "esse", "ja", "gern", "räucherschinken"]
      trg_sentence = ["i", "love", "to", "eat", "smoked", "ham"]
      corpus = [AlignedSent(trg_sentence, src_sentence)]
      alignment_info = AlignmentInfo(
          (0, 1, 4, 0, 2, 5, 5),
          [None] + src_sentence,
          ["UNUSED"] + trg_sentence,
          None,
      )
  
      translation_table = defaultdict(lambda: defaultdict(float))
      translation_table["i"]["ich"] = 0.98
      translation_table["love"]["gern"] = 0.98
      translation_table["to"][None] = 0.98
      translation_table["eat"]["esse"] = 0.98
      translation_table["smoked"]["räucherschinken"] = 0.98
      translation_table["ham"]["räucherschinken"] = 0.98
  
      model1 = IBMModel1(corpus, 0)
      model1.translation_table = translation_table
  
      # act
      probability = model1.prob_t_a_given_s(alignment_info)
  
      # assert
      lexical_translation = 0.98 * 0.98 * 0.98 * 0.98 * 0.98 * 0.98
      expected_probability = lexical_translation
      self.assertEqual(
          round(probability, 4), round(expected_probability, 4)
      )
  
file_path: nltk/nltk/test/unit/translate/test_ibm1.py
imports: import unittest
  from collections import defaultdict
  from nltk.translate import AlignedSent, IBMModel, IBMModel1
  from nltk.translate.ibm_model import AlignmentInfo
label_desc: Use image node_id 3 for calling the TestIBMModel1 obj's underlying member method code with example usage: obj.test_prob_t_a_given_s() without return types