**Use case**
I'm using `ip_trie` on maxmind geoip databases. Given an IP address I want to find out what key was used (ie what network the IP comes under). But it seems it is not possible to look up the key field when using `dictGet`?

```
        <layout>
            <ip_trie/>
        </layout>
        <structure>
            <key>
                <attribute>
                    <name>network</name>
                    <type>String</type>
                </attribute>
            </key>
            <attribute>
                <name>geoname_id</name>
                <type>UInt32</type>
                <null_value>0</null_value>
            </attribute>
...
```

```
clickhouse :) select dictGet('geoip_city_blocks_ipv4', 'geoname_id', tuple(toUInt32(toIPv4('1.1.1.1')))) ;

┌─dictGet('geoip_city_blocks_ipv4', 'geoname_id', tuple(toUInt32(toIPv4('1.1.1.1'))))─┐
│                                                                             2077456 │
└─────────────────────────────────────────────────────────────────────────────────────┘

clickhouse :) select dictGet('geoip_city_blocks_ipv4', 'network', tuple(toUInt32(toIPv4('1.1.1.1')))) ;

Received exception from server (version 20.11.3):
Code: 36. DB::Exception: Received from localhost:9000. DB::Exception: No such attribute 'network': While processing dictGet('geoip_city_blocks_ipv4', 'network', tuple(toUInt32(toIPv4('1.1.1.1')))). 
```

{
    return row_idx.end();
}
IPAddressDictionary::RowIdxConstIter IPAddressDictionary::tryLookupIPv4(UInt32 addr, uint8_t * buf) const
{
    if (std::get_if<IPv6Container>(&ip_column))
    {
        mapIPv4ToIPv6(addr, buf);
        return lookupIP<IPv6Container>(buf);
    }
    return lookupIP<IPv4Container>(addr);
}
IPAddressDictionary::RowIdxConstIter IPAddressDictionary::tryLookupIPv6(const uint8_t * addr) const
{
    if (std::get_if<IPv4Container>(&ip_column))
    {
        bool is_mapped = false;
        UInt32 addrv4 = mappedIPv4ToBinary(addr, is_mapped);
        if (!is_mapped)
            return ipNotFound();
        return lookupIP<IPv4Container>(addrv4);
    }
    return lookupIP<IPv6Container>(addr);
}
template <typename IPContainerType, typename IPValueType>
IPAddressDictionary::RowIdxConstIter IPAddressDictionary::lookupIP(IPValueType target) const