def bestseqs(self,thresh=None):
        """
        m.bestseqs(,thresh=None)  -- Return all k-mers that match motif with a score >= thresh
        """
        if not thresh:
            if self._bestseqs:
                return self._bestseqs
        if not thresh: thresh = 0.8 * self.maxscore
        self._bestseqs = bestseqs(self,thresh)
        return self._bestseqs