docs: def diff(a, b):
      """
      Performs a longest common substring diff.
  
      :Parameters:
          a : sequence of `comparable`
              Initial sequence
          b : sequence of `comparable`
              Changed sequence
  
      :Returns:
          An `iterable` of operations.
      """
      a, b = list(a), list(b)
      opcodes = SM(None, a, b).get_opcodes()
      return parse_opcodes(opcodes)