错误：spawn.py, line 134, in _check_not_importing_main

错误信息：

Python\Python38\lib\multiprocessing\spawn.py", line 134, in _check_not_importing_main
    raise RuntimeError('''
RuntimeError:
        An attempt has been made to start a new process before the
        current process has finished its bootstrapping phase.

        This probably means that you are not using fork to start your
        child processes and you have forgotten to use the proper idiom
        in the main module:

            if __name__ == '__main__':
                freeze_support()
                ...

        The "freeze_support()" line can be omitted if the program
        is not going to be frozen to produce an executable.
 

原来的代码：

# 省略一些代码...
results = model.train(data='coco128.yaml', epochs=3)

解决：

把相应的代码移到main中，例如：

def test():
    # 省略一些代码...
    results = model.train(data='coco128.yaml', epochs=3)
    # ...

if __name__ == '__main__':
    test()