input: Write a python function to find all palindromic substrings of length 3 and 4 from a given string.
  assert palindromic_substring("abc") == []
  assert palindromic_substring("abccba") == ['bccb']
  assert palindromic_substring("abacdcabbd") == ['aba', 'cdc', 'abba']
  assert palindromic_substring("abbaaccadda") == ['aba', 'adda']
output: def palindromic_substring(s):
      def is_palindrome(sub):
          return sub == sub[::-1]
  
      result = []
      n = len(s)
      
      for i in range(n):
          if i + 3 <= n and is_palindrome(s[i:i+3]):
              result.append(s[i:i+3])
          if i + 4 <= n and is_palindrome(s[i:i+4]):
              result.append(s[i:i+4])
      
      return result