**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')))). 
```

{
            if (isv6)
                return reinterpret_cast<const uint8_t *>(addr.addr());
            memset(buf, 0, 10);
            buf[10] = '\xFF';
            buf[11] = '\xFF';
            memcpy(&buf[12], addr.addr(), 4);
            return buf;
        }
        inline UInt8 prefixIPv6() const
        {
            return isv6 ? prefix : prefix + 96;
        }
    };
    struct IPv4Subnet
    {
        UInt32 addr;
        UInt8 prefix;
    };
    struct IPv6Subnet
    {
        const uint8_t * addr;
        UInt8 prefix;
    };
}
static std::pair<Poco::Net::IPAddress, UInt8> parseIPFromString(const std::string_view addr_str)