How can i find some fields?

first of all, please understand my poor English. Because I’m not live in English-speaking country.
I’m interested in Bro and Bro scripts nowadays. It’s very flexible.
But, I don’t know how to create a module’s fields. For example, DNS module in bro has some fields of “Info”.

===================== base/protocols/dns/main.bro
module DNS;

export {

The DNS logging stream identifier.

redef enum Log::ID += { LOG };

The record type which contains the column fields of the DNS log.

type Info: record {

The earliest time at which a DNS protocol message over the

associated connection is observed.

ts: time &log;

A unique identifier of the connection over which DNS messages

are being transferred.

uid: string &log;

The connection’s 4-tuple of endpoint addresses/ports.

id: conn_id &log;

The transport layer protocol of the connection.

proto: transport_proto &log;

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