code: def is_stopword_record(self, record):
          
          # preserve negations
          if record.root == 'ない':
              return False
          return (
              record.pos in STOPWORD_CATEGORIES or
              record.subclass1 in STOPWORD_CATEGORIES or
              record.root in STOPWORD_ROOTS
          )
docs: Determine whether a single MeCab record represents a stopword.
  
          This mostly determines words to strip based on their parts of speech.
          If common_words is set to True (default), it will also strip common
          verbs and nouns such as くる and よう. If more_stopwords is True, it
          will look at the sub-part of speech to remove more categories.