code: def test_lr_bigram(self):
      self.assertAlmostEqual(
          BigramAssocMeasures.likelihood_ratio(2, (4, 4), 20),
          2.4142743368419755,
          delta=_DELTA,
      )
      self.assertAlmostEqual(
          BigramAssocMeasures.likelihood_ratio(1, (1, 1), 1),
          0.0,
          delta=_DELTA,
      )
      self.assertRaises(
          ValueError,
          BigramAssocMeasures.likelihood_ratio,
          *(0, (2, 2), 2),
      )
  
imports: import unittest
  from nltk.metrics import BigramAssocMeasures, QuadgramAssocMeasures, TrigramAssocMeasures
label_desc: Use image node_id 1 for calling the TestLikelihoodRatio obj's underlying member method code with example usage: obj.test_lr_bigram() without return types