docs: def _load_cookie(self):
          """Loads HTTP Cookie from environ"""
  
          cookie = SimpleCookie(self._environ.get('HTTP_COOKIE'))
          vishnu_keys = [key for key in cookie.keys() if key == self._config.cookie_name]
  
          # no session was started yet
          if not vishnu_keys:
              return
  
          morsel = cookie[vishnu_keys[0]]
          morsel_value = morsel.value
  
          if self._config.encrypt_key:
              cipher = AESCipher(self._config.encrypt_key)
              morsel_value = cipher.decrypt(morsel_value)
  
          received_sid = Session.decode_sid(self._config.secret, morsel_value)
          if received_sid:
              self._sid = received_sid
          else:
              logging.warn("found cookie with invalid signature")