input: def has_duplicate_substring(s: str) -> bool:
      """
      Given a string s, determine if there is any substring of length 2 that appears in the reverse of s.
  
      Return true if such a substring exists, otherwise return false.
  
      Examples:
      >>> s = "leetcode"
      true
      >>> s = "abcba"
      true
      >>> s = "abcd"
      false
  
      Constraints:
      1 <= s.length <= 100
      s contains only lowercase English letters.
      """
output:     reversed_s = s[::-1]
      for i in range(len(s) - 1):
          if s[i:i+2] in reversed_s:
              return True
      return False