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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 set_tcp_md5sig(s, addr, key):
 """Enable TCP-MD5 on the given socket. :param s: Socket :param addr: Associated address. On some platforms, this has no effect. :param key: Key. On some platforms, this has no effect. """

    impls = {
        'FreeBSD': _set_tcp_md5sig_bsd,
        'Linux': _set_tcp_md5sig_linux,
        'NetBSD': _set_tcp_md5sig_bsd,
    }
    system = platform.system()
    try:
        impl = impls[system]
    except KeyError:
        raise NotImplementedError("TCP-MD5 unsupported on this platform")
    impl(s, addr, key)