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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def was_init():
 """This function returns the subsystems which have previously been initialized. Returns: Set[InitFlag]: Flags indicating which subsystems have been initialized. """

    mask = lib.SDL_WasInit(0)
    return enumtools.get_items(InitFlags, mask, {InitFlags.everything})