code: def ssh_check_mic(self, mic_token, session_id, username=None):
          
          self._session_id = session_id
          self._username = username
          if username is not None:
              # server mode
              mic_field = self._ssh_build_mic(
                  self._session_id,
                  self._username,
                  self._service,
                  self._auth_method,
              )
              # Verifies data and its signature.  If verification fails, an
              # sspi.error will be raised.
              self._gss_srv_ctxt.verify(mic_field, mic_token)
          else:
              # for key exchange with gssapi-keyex
              # client mode
              # Verifies data and its signature.  If verification fails, an
              # sspi.error will be raised.
              self._gss_ctxt.verify(self._session_id, mic_token)
docs: Verify the MIC token for a SSH2 message.
  
          :param str mic_token: The MIC token received from the client
          :param str session_id: The SSH session ID
          :param str username: The name of the user who attempts to login
          :return: None if the MIC check was successful
          :raises: ``sspi.error`` -- if the MIC check failed