code: def set_background_corpus(self, background):
          '''
          Parameters
          ----------
          background
  
          '''
          if issubclass(type(background), TermDocMatrixWithoutCategories):
              self._background_corpus = pd.DataFrame(background
                                                     .get_term_freq_df()
                                                     .sum(axis=1),
                                                     columns=['background']).reset_index()
              self._background_corpus.columns = ['word', 'background']
          elif (type(background) == pd.DataFrame
                and set(background.columns) == set(['word', 'background'])):
              self._background_corpus = background
          else:
              raise Exception('The argument named background must be a subclass of TermDocMatrix or a ' \
                              + 'DataFrame with columns "word" and "background", where "word" ' \
                              + 'is the term text, and "background" is its frequency.'f set_background_corpus(self, background):
          '''
          Parameters
          ----------
          background
  
          '''
          if issubclass(type(background), TermDocMatrixWithoutCategories):
              self._background_corpus = pd.DataFrame(background
                                                     .get_term_freq_df()
                                                     .sum(axis=1),
                                                     columns=['background']).reset_index()
              self._background_corpus.columns = ['word', 'background']
          elif (type(background) == pd.DataFrame
                and set(background.columns) == set(['word', 'background'])):
              self._background_corpus = background
          else:
              raise Exception('The argument named background must be a subclass of TermDocMatrix or a ' \
                              + 'DataFrame with columns "word" and "background", where "word" ' \
                              + 'is the term text, and "background" is its frequency.')
docs: Parameters
          ----------
          background