def __iadd__(self, target):
        ''' use this to combine databases '''
        assert isinstance(target, RamGraphDB), 'graph databases can only be added to other graph databases'
        for src, name, dst in target.list_relations():
            self.store_relation(src, name, dst)
        return self
def __iadd__ ( self , target ) : assert isinstance ( target , RamGraphDB ) , 'graph databases can only be added to other graph databases' for src , name , dst in target . list_relations ( ) : self . store_relation ( src , name , dst ) return self
use this to combine databases