input: def has_common_substring(s: str) -> bool:
      """
      Given a string s, identify if any 2-character substring in s appears in the reverse of s.
  
      Return true if such a substring is found, otherwise return false.
  
      Examples:
      >>> s = "leetcode"
      true
      >>> s = "abcba"
      true
      >>> s = "abcd"
      false
  
      Constraints:
      1 <= s.length <= 100
      s consists only of lowercase English letters.
      """
output:     
      substr_set = set()
  
      for i in range(len(s) - 1):
          substr_set.add(s[i:i+2])
  
      s_reversed = s[::-1]
  
      for i in range(len(s_reversed) - 1):
          if s_reversed[i:i+2] in substr_set:
              return True
  
      return False
  