def METHOD_NAME(self, div):
    """
    For performance reasons, we cache these results in a dict indexed by
    (organisation_id, divisionset.start_date)
    This means we only need to do one round-trip to the DB per DivisionSet
    instead of once per division. This speeds things up a bit.
    """
    if (
        div.organisation_id,
        div.divisionset.start_date,
    ) in self.org_boundaries:
        return self.org_boundaries[
            (div.organisation_id, div.divisionset.start_date)
        ]
    org = Organisation.objects.get(pk=div.organisation_id).get_geography(
        div.divisionset.start_date
    )
    self.org_boundaries[
        (div.organisation_id, div.divisionset.start_date)
    ] = org
    return org