Load a single row of data and convert it into entities and
        relations.

def load(self, data):
        """ Load a single row of data and convert it into entities and
        relations. """
        objs = {}
        for mapper in self.entities:
            objs[mapper.name] = mapper.load(self.loader, data)

        for mapper in self.relations:
            objs[mapper.name] = mapper.load(self.loader, data, objs)