How to use the textdistance.utils.find_ngrams function in textdistance

def _get_sequences(self, *sequences):
        """Prepare sequences.

        qval=None: split text by words
        qval=1: do not split sequences. For text this is mean comparing by letters.
        qval>1: split sequences by q-grams
        """
        # by words
        if not self.qval:
            return [s.split() for s in sequences]
        # by chars
        if self.qval == 1:
            return sequences
        # by n-grams
        return [find_ngrams(s, self.qval) for s in sequences]

def _custom(self, *sequences):
        short = min(sequences, key=len)
        length = len(short)
        for n in range(length, 0, -1):
            for subseq in find_ngrams(short, n):
                subseq = ''.join(subseq)
                for seq in sequences:
                    if subseq not in seq:
                        break
                else:
                    return subseq
        return type(short)()  # empty sequence