def METHOD_NAME(self, rom):
    info = self.entrance_info
    re = RoomEditor(rom, info.alt_room if info.alt_room is not None else info.room)
    self.source_warp = re.getWarps()[info.index if info.index not in (None, "all") else 0]
    re = RoomEditor(rom, self.source_warp.room)
    for idx, warp in enumerate(re.getWarps()):
        if warp.room == info.room or warp.room == info.alt_room:
            self.target_warp_idx = idx