code: def lcsr(s1, s2):
      '''longest common sequence ratio
  
      >>> lcsr('ab', 'abcd')
      0.5
      '''
      if s1 == s2:
          return 1.0
      return llcs(s1, s2) / max(1, len(s1), len(s2)f lcsr(s1, s2):
      '''longest common sequence ratio
  
      >>> lcsr('ab', 'abcd')
      0.5
      '''
      if s1 == s2:
          return 1.0
      return llcs(s1, s2) / max(1, len(s1), len(s2))
docs: longest common sequence ratio
  
      >>> lcsr('ab', 'abcd')
      0.5