def load_connection_file(self):
        """load connection info from JSON dict in self.connection_file"""
        with open(self.connection_file) as f:
            cfg = json.loads(f.read())
        
        self.ip = cfg['ip']
        self.shell_port = cfg['shell_port']
        self.stdin_port = cfg['stdin_port']
        self.iopub_port = cfg['iopub_port']
        self.hb_port = cfg['hb_port']
        self.session.key = str_to_bytes(cfg['key'])
load connection info from JSON dict in self.connection_file