How to use the census.core.APIKeyError function in census

'get': ",".join(fields),
            'for': geo['for'],
            'key': self._key,
        }

        if 'in' in geo:
            params['in'] = geo['in']

        resp = self.session.get(url, params=params)

        if resp.status_code == 200:
            try:
                data = resp.json()
            except ValueError as ex:
                if '<title>Invalid Key</title>' in resp.text:
                    raise APIKeyError(' '.join(resp.text.splitlines()))
                else:
                    raise ex

            headers = data.pop(0)
            types = [self._field_type(header, year) for header in headers]
            results = [{header : (cast(item) if item is not None else None)
                        for header, cast, item
                        in zip(headers, types, d)}
                       for d in data]
            return results

        elif resp.status_code == 204:
            return []

        else:
            raise CensusException(resp.text)