python代码有一行标黄

def do_telnet(Host, username, password, terminal, command):
    '''
    :param Host: ip
    :param username:用户名
    :param password: 密码
    :param terminal: 终端命令行
    :param command: 命令
    :return:
    '''
 
    # 连接Telnet服务器
    tn=telnetlib.Telnet(Host,23)
 
    tn.read_until(b'user: ')
    tn.write(username.encode('ascii') + b'\n')
 
    tn.read_until(b'password:')
    tn.write(password.encode('ascii') + b'\n')
 
    # 登录完毕后执行命令，e-高级
    tn.read_until(terminal)
    tn.write(b'%s\n' % command)
    time.sleep(1)
    result_a = tn.read_very_eager().decode('gbk')
    #print(result_a+'\n',type(result_a))
 
    # 显示协议报文列表
    tn.write(b'%s\n' % Get_Number(result_a))
    time.sleep(1)
    pro_result = tn.read_very_eager().decode('gbk')
    # print(pro_result+'\n',type(pro_result))
 
    return output_df(pro_result, Host)
    
    tn.close()  # tn.write('exit\n')   # 执行完毕后，终止Telnet连接（或输入exit退出）