code: def test_filter_bigrams_by_pmis(self):
      term_doc_mat = get_hamlet_term_doc_matrix()
      df = term_doc_mat.get_term_freq_df()
      filtered_df = filter_bigrams_by_pmis(df, threshold_coef=3)
      self.assertLess(len(filtered_df), len(df))
  
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 3 for calling the TestPMIFiltering obj's underlying member method code with example usage: obj.test_filter_bigrams_by_pmis() without return types