input: def optimize_reverse_string(reverse_string_func):
      """
      Given a function that reverses a string using a loop, optimize it to reverse the string using slicing.
      
      >>> optimize_reverse_string(lambda s: ''.join(c for c in s[::-1]))
      'lambda s: s[::-1]'
      """
      return lambda s: s[::-1]
output:     return lambda s: s[::-1]