def _existing_terms(self, ixreader, termset, reverse=False, phrases=True):
        if phrases:
            fieldname = self.fieldname
            fieldnum = ixreader.fieldname_to_num(fieldname)
            for word in self.words:
                contains = (fieldnum, word) not in ixreader
                if reverse: contains = not contains
                if contains:
                    termset.add((fieldname, word))
dataset/ETHPy150Open dokipen/whoosh/src/whoosh/query.py/Phrase._existing_terms/operator `in` -> `not in`