def iter_prefix(self, fieldid, prefix):
        
        fieldid = self.schema.to_number(fieldid)
        for fn, t, docfreq, colfreq in self.iter_from(fieldid, prefix):
            if fn != fieldid or not t.startswith(prefix):
                return
            yield (t, docfreq, colfreq)
Yields (field_num, text, doc_freq, index_freq) tuples
dataset/ETHPy150Open dokipen/whoosh/src/whoosh/reading.py/IndexReader.iter_prefix