code: def unshorten(self, uri: str) -> str:
          
          res = self.get(uri)
  
          ysmm = re.findall(r'var ysmm =.*\;?', res.text)
  
          if len(ysmm) == 0:
              raise UnshortenFailed('No ysmm variable found.')
  
          # Decode the ysmm variable and extract the actual link
          ysmm = re.sub(r'var ysmm \= \'|\'\;', '', ysmm[0])
  
          left = ''
          right = ''
  
          for c in [ysmm[i:i+2] for i in range(0, len(ysmm), 2)]:
              left += c[0]
              right = c[1] + right
  
          # Additional digit arithmetic
          encoded_uri = list(left + right)
          numbers = ((i, n) for i, n in enumerate(encoded_uri) if str.isdigit(n))
          for first, second in zip(numbers, numbers):
              xor = int(first[1]) ^ int(second[1])
              if xor < 10:
                  encoded_uri[first[0]] = str(xor)
  
          decoded_uri = b64decode("".join(encoded_uri).encode())[16:-16].decode()
  
          if re.search(r'go\.php\?u\=', decoded_uri):
              decoded_uri = b64decode(re.sub(r'(.*?)u=', '', decoded_uri)).decode()
  
          return decoded_uri
docs: http://j.gs/AXr9