local variable 'excel_instance' referenced before assignment

 local variable 'excel_instance' referenced before assignment
Traceback (most recent call last):
File "C:\Program Files (x86)\ShadowBot\shadowbot-5.13.33\python\lib\runpy.py", line 193, in _run_module_as_main
"__main__", mod_spec)
File "C:\Program Files (x86)\ShadowBot\shadowbot-5.13.33\python\lib\runpy.py", line 85, in _run_code
exec(code, run_globals)
File "C:\Program Files (x86)\ShadowBot\shadowbot-5.13.33\python\lib\site-packages\xbot_interpreter.py", line 94, in <module>
main()
File "C:\Program Files (x86)\ShadowBot\shadowbot-5.13.33\python\lib\site-packages\xbot_interpreter.py", line 55, in main
mod.main(args)
File "C:\Users\zhang\AppData\Local\ShadowBot\users\603214531759157250\apps\98d5e621-9b9c-4074-b022-7816d24be08c\xbot_robot\main.py", line 21, in main
xbot_visual.excel.active(workbook=excel_instance, mode="index", value="2", _block=("main", 13, "激活Sheet页"))
UnboundLocalError: local variable 'excel_instance' referenced before assignment