code: def set_seq2(self, b):
          
  
          if b is self.b:
              return
          self.b = b
          self.matching_blocks = self.opcodes = None
          self.fullbcount = None
          self.__chain_b()
docs: Set the second sequence to be compared.
  
          The first sequence to be compared is not changed.
  
          >>> s = SequenceMatcher(None, "abcd", "bcde")
          >>> s.ratio()
          0.75
          >>> s.set_seq2("abcd")
          >>> s.ratio()
          1.0
          >>>
  
          SequenceMatcher computes and caches detailed information about the
          second sequence, so if you want to compare one sequence S against
          many sequences, use .set_seq2(S) once and call .set_seq1(x)
          repeatedly for each of the other sequences.
  
          See also set_seqs() and set_seq1().