def set_initialize_mode(complexity=2):
        """Set initialization mode. Default is slow mode.
        
        **中文文档**
        
        设置WinFile类的全局变量, 指定WinFile.initialize方法所绑定的初始化方式。
        """
        if complexity == 3:
            WinFile.initialize = WinFile.level3_initialize
            WinFile.init_mode = 3
        elif complexity == 2:
            WinFile.initialize = WinFile.level2_initialize
            WinFile.init_mode = 2
        elif complexity == 1:
            WinFile.initialize = WinFile.level1_initialize
            WinFile.init_mode = 1
        else:
            raise ValueError("complexity has to be 3, 2 or 1.")