code: def is_verified(self):
          
          if self._verified is None:
              signature = self._data.get('Signature')
              if not signature:
                  self._verified = False
                  return self._verified
  
              # Decode the signature from base64
              signature = bytes(base64.b64decode(signature))
  
              # Get the message to sign
              sign_bytes = self._get_bytes_to_sign()
              if not sign_bytes:
                  self._verified = False
                  return self._verified
  
              if not self.certificate:
                  self._verified = False
                  return self._verified
  
              # Extract the public key
              pkey = self.certificate.get_pubkey()
  
              # Use the public key to verify the signature.
              pkey.verify_init()
              pkey.verify_update(sign_bytes)
              verify_result = pkey.verify_final(signature)
  
              self._verified = verify_result == 1
  
          return self._verified
docs: Verifies an SES bounce message.