[ERROR] [1703057964.784450]: bad callback: <function laser_callback at 0x7fc4bb4d6700>

[Xizhe-Hao]

xizhe@ubuntu:~/Downloads/tb3_nav_multi_point-main$ /bin/python3 /home/xizhe/Downloads/tb3_nav_multi_point-main/tb3_nav_multi_point_and_polec/main.py
[ERROR] [1703057964.784450]: bad callback: <function laser_callback at 0x7fc4bb4d6700>
Traceback (most recent call last):
  File "/opt/roseticb/python3/dist-packages/rospy/topics.py", line 750, in _invoke_callback
    cb(msg)
  File "/home/xizhe/Downloads/tb3_nav_multi_point-main/tb3_nav_multi_point_and_polec/main.py", line 60, in laser_callback
    print('cb:',flag)
UnboundLocalError: local variable 'flag' referenced before assignment

Traceback (most recent call last):
  File "/home/xizhe/Downloads/tb3_nav_multi_point-main/tb3_nav_multi_point_and_polec/main.py", line 102, in <module>
    result = movebase_client()
  File "/home/xizhe/Downloads/tb3_nav_multi_point-main/tb3_nav_multi_point_and_polec/main.py", line 54, in movebase_client
    if not flag:
UnboundLocalError: local variable 'flag' referenced before assignment