我有 Ubuntu 16.04 Xenial Xerus，当我想运行sudo apt-get updateorsudo apt-get autoclean或sudo apt-get install (package name)or 时sudo apt-get install -f，我收到以下消息：
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W: Target Packages (main/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list:2 and /etc/apt/sources.list:5
W: Target Packages (main/binary-i386/Packages) is configured multiple times in /etc/apt/sources.list:2 and /etc/apt/sources.list:5
W: Target Packages (main/binary-all/Packages) is configured multiple times in /etc/apt/sources.list:2 …apt ×1