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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 _subnets(proto='inet', interfaces_=None):
    '''
    Returns a list of subnets to which the host belongs
    '''
    if interfaces_ is None:
        ifaces = interfaces()
    elif isinstance(interfaces_, list):
        ifaces = {}
        for key, value in six.iteritems(interfaces()):
            if key in interfaces_:
                ifaces[key] = value
    else:
        ifaces = {interfaces_: interfaces().get(interfaces_, {})}

    ret = set()

    if proto == 'inet':
        subnet = 'netmask'
        dflt_cidr = 32
    elif proto == 'inet6':
        subnet = 'prefixlen'
        dflt_cidr = 128
    else:
        log.error('Invalid proto %s calling subnets()', proto)
        return

    for ip_info in six.itervalues(ifaces):
        addrs = ip_info.get(proto, [])
        addrs.extend([addr for addr in ip_info.get('secondary', []) if addr.get('type') == proto])

        for intf in addrs:
            if subnet in intf:
                intf = ipaddress.ip_interface('{0}/{1}'.format(intf['address'], intf[subnet]))
            else:
                intf = ipaddress.ip_interface('{0}/{1}'.format(intf['address'], dflt_cidr))
            if not intf.is_loopback:
                ret.add(intf.network)
    return [six.text_type(net) for net in sorted(ret)]