class_docstr: Designed for use only in the term_scorer argument.
  This should really be inherit specific type.
  
  term_scorer = (BM25Difference(corpus, k1 = 1.4, b=0.9)
          .set_categories('Positive', ['Negative'], ['Plot']))
  
  html = st.produce_frequency_explorer(
          corpus,
          category='Positive',
          not_categories=['Negative'],
          neutral_categories=['Plot'],
          term_scorer=term_scorer,
          metadata=rdf['movie_name'],
          grey_threshold=0,
          show_neutral=True
  )
  file_name = 'output/rotten_fresh_bm25.html'
  open(file_name, 'wb').write(html.encode('utf-8'))
  IFrame(src=file_name, width=1300, height=700)
code: def get_name(self):
      return "BM25 difference"
  
imports: import numpy
  from scattertext.termscoring.CorpusBasedTermScorer import CorpusBasedTermScorer
label_desc: Use image node_id 3 for calling the BM25Difference obj's underlying member method code with example usage: obj.get_name() and returns: str