Get the latest data from api.entur.org.

async def update(self) -> None:
        """Get the latest data from api.entur.org."""
        headers = {'ET-Client-Name': self._client_name}
        request = {
            'query': self.get_gql_query(),
            'variables': {
                'stops': self.stops,
                'quays': self.quays,
                'whitelist': {
                    'lines': self.line_whitelist
                },
                'numberOfDepartures': self.number_of_departures,
                'omitNonBoarding': self.omit_non_boarding
            }
        }

        with async_timeout.timeout(10):
            resp = await self.web_session.post(RESOURCE,
                                               json=request,
                                               headers=headers)

        if resp.status != 200:
            _LOGGER.error(
                "Error connecting to Entur, response http status code: %s",
                resp.status)
            return None

        result = await resp.json()

        if 'errors' in result:
            _LOGGER.warning("Entur API responded with error message: {error}",
                            result['errors'])
            return

        self._data = result['data']

        if 'stopPlaces' in self._data:
            for stop in self._data['stopPlaces']:
                self._process_place(stop, False)

        if 'quays' in self._data:
            for quay in self._data['quays']:
                self._process_place(quay, True)