class_docstr: Reduce corpus to the X most important terms.  Great for plotting a big corpus.
  Will return between X/2 and X terms.
  
  Returns the terms with the X highest absolute scores, background corpus scores, and term frequencies.
code: def _get_frequent_terms(num_term_to_keep, term_doc_freq):
      return (
          term_doc_freq.sort_values(by="count", ascending=False)
          .iloc[: int(0.125 * num_term_to_keep)]
          .index
      )
  
label_desc: Use image node_id 3 for calling the AutoTermSelector obj's underlying member method code with example usage: obj._get_frequent_terms(num_term_to_keep, term_doc_freq) and returns: term_doc_freq