ImportError: cannot import name 'BASE_DIR'但是不影响运行，这是什么原因？

Question

debug结果如下：Connected to pydev debugger (build 191.6183.50)Traceback (most recent call last):  File "D:\Program Files\Pycharm\PyCharm 2019.1\helpers\pydev\pydevd.py", line 1741, in <module>    main()  File "D:\Program Files\Pycharm\PyCharm 2019.1\helpers\pydev\pydevd.py", line 1735, in main    globals = debugger.run(setup['file'], None, None, is_module)  File "D:\Program Files\Pycharm\PyCharm 2019.1\helpers\pydev\pydevd.py", line 1135, in run    pydev_imports.execfile(file, globals, locals)  # execute the script  File "D:\Program Files\Pycharm\PyCharm 2019.1\helpers\pydev\_pydev_imps\_pydev_execfile.py", line 18, in execfile    exec(compile(contents+"\n", file, 'exec'), glob, loc)  File "C:/Users/Sulod/Networks/VRPTW_GA/gavrptw/core.py", line 10, in <module>    from . import BASE_DIRImportError: cannot import name 'BASE_DIR'Process finished with exit code -1