def lookup(self, keys, read_consistency=None, transaction=None):
        """
        
        """
        conn = self.get_conn()

        body = {'keys': keys}
        if read_consistency:
            body['readConsistency'] = read_consistency
        if transaction:
            body['transaction'] = transaction
        resp = (conn
                .projects()
                .lookup(projectId=self.project_id, body=body)
                .execute(num_retries=self.num_retries))

        return resp