How to use the census.core.SF3Client function in census

within = 'state:{state} county:{county} tract:{tract}'.format(**context)

            block_id = block['properties']['BLOCK']
            result = self.get(fields,
                              {'for': 'block:{}'.format(block_id),
                               'in' :  within}, year)

            if result:
                result, = result
            else:
                result = {}

            yield block, result, intersection_proportion


class SF3Client(census.core.SF3Client, GeoClient):
    @supported_years(2000, 1990)
    def state_place_tract(self, *args, **kwargs):
        return self._state_place_area(self.geo_tract, *args, **kwargs)

    @supported_years(2000)
    def state_place_blockgroup(self, *args, **kwargs):
        return self._state_place_area(self.geo_blockgroup, *args, **kwargs)

class Census(census.Census):
    def __init__(self, key, year=None, session=None):
        super(Census, self).__init__(key, year, session)
        self.acs5 = ACS5Client(key, year, session)
        self.sf1 = SF1Client(key, year, session)
        self.sf3 = SF3Client(key, year, session)

self.session = session
        self.session.headers.update({
            'User-Agent': ('python-census/{} '.format(__version__) +
                           'github.com/datamade/census')
        })

        self._acs = ACS5Client(key, year, session)  # deprecated
        self.acs5 = ACS5Client(key, year, session)
        self.acs3 = ACS3Client(key, year, session)
        self.acs1 = ACS1Client(key, year, session)
        self.acs5dp = ACS5DpClient(key, year, session)
        self.acs3dp = ACS3DpClient(key, year, session)
        self.acs1dp = ACS1DpClient(key, year, session)
        self.sf1 = SF1Client(key, year, session)
        self.sf3 = SF3Client(key, year, session)