实验性实验性Adds a callback that will be called before a players game mode is changed.
无法在只读模式下调用此函数，详见 WorldBeforeEvents。
This function can be called in early-execution mode.
实验性Removes a callback from being called before a players game mode is changed.
无法在只读模式下调用此函数，详见 WorldBeforeEvents。
This function can be called in early-execution mode.
Manages callbacks that are connected to before a players game mode is changed.