code: def test_unigrams_that_only_occur_in_one_bigram(self):
      bigrams = set(
          [
              "the cat",
              "the saw",
              "horses are",
              "are pigs",
              "pigs horses",
          ]
      )
      expected = {"cat", "saw"}
      self.assertEqual(
          expected, unigrams_that_only_occur_in_one_bigram(bigrams)
      )
  
file_path: scattertext/scattertext/test/test_PMIFiltering.py
imports: from unittest import TestCase
  import pandas
  from scattertext import TermDocMatrixFilter
  from scattertext import TermDocMatrixFromPandas
  from scattertext import whitespace_nlp
  from scattertext.TermDocMatrixFilter import AtLeastOneCategoryHasNoTermsException, filter_bigrams_by_pmis, unigrams_that_only_occur_in_one_bigram, filter_out_unigrams_that_only_occur_in_one_bigram
  from scattertext.test.test_TermDocMat import get_hamlet_term_doc_matrix
label_desc: Use image node_id 4 for calling the TestPMIFiltering obj's underlying member method code with example usage: obj.test_unigrams_that_only_occur_in_one_bigram() without return types