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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 add_port_fwd(zone, src, dest, proto='tcp', dstaddr='', permanent=True):
    '''
    Add port forwarding.

    .. versionadded:: 2015.8.0

    CLI Example:

    .. code-block:: bash

        salt '*' firewalld.add_port_fwd public 80 443 tcp
    '''
    cmd = '--zone={0} --add-forward-port=port={1}:proto={2}:toport={3}:toaddr={4}'.format(
        zone,
        src,
        proto,
        dest,
        dstaddr
    )

    if permanent:
        cmd += ' --permanent'

    return __firewall_cmd(cmd)