def _find_primary_key_columns(self, table_name):
        db_name = self._get_setting('NAME')
        
        primary_key_columns = set()
        for col, constraints in self.lookup_constraint(db_name, table_name):
            for kind, cname in constraints:
                if kind == 'PRIMARY KEY':
                    primary_key_columns.add(col.lower())
                    
        return primary_key_columns
Writes the nodes info to confi file in yaml format.
dataset/ETHPy150Open cloudera/hue/desktop/core/ext-py/South-1.0.2/south/db/generic.py/DatabaseOperations._find_primary_key_columns--crossover with--dataset/ETHPy150Open Havate/havate-openstack/proto-build/gui/horizon/Horizon_GUI/openstack_dashboard/static-raw/scripts/SPConsumer.py/Openstack.addHost