code: def best_match(self, seqs, scan_rc=True):
          
          self.set_threshold(threshold=0.0)
          for matches in self.scan(seqs, 1, scan_rc):
              yield [m[0] for m in matches]
docs: give the best match of each motif in each sequence
          returns an iterator of nested lists containing tuples:
          (score, position, strand)