How to use the pg-promise.txMode function in pg-promise

import * as lib from "pg-promise";

var pgp = lib({
    capSQL: true,
    pgFormatting: true,
    pgNative: true
});

interface Test {
    hello:string;
}

var db = pgp('connection');

var txMode = new lib.txMode.TransactionMode();

function myTransaction(t) {
}

myTransaction['txMode'] = txMode;

db.tx(function (t) {
    var w = t.one('');
    var q = t.hello;
});

return final + pgp.queryResult[mask]
    }, 0)

    if (script.transaction) {
      if (typeof script.transaction !== 'object') {
        script.transaction = {}
      }

      if (!script.transaction.tag) {
        script.transaction.tag = script.name
      }

      if (script.transaction.isolation) {
        assert(pgp.txMode.isolationLevel.hasOwnProperty(script.transaction.isolation), `Script at ${path} specified invalid transaction isolation level "${script.transaction.isolation}"`)
      }
      script.transaction.mode = new pgp.txMode.TransactionMode(script.transaction.isolation, script.transaction.readOnly, script.transaction.deferrable)

      script.transaction.options = {
        tag: script.transaction.tag,
        mode: script.transaction.mode
      }

      if (typeof script.execute === 'function') {
        const userFn = script.execute
        script.execute = (arg) => {
          return db.tx(script.transaction.options, (d) => userFn(d, arg))
        }
      } else {
        assert(typeof script.query === 'string', `Script at ${path} must specify a "query" property`)
        script.execute = (arg) => {
          return db.tx(script.transaction.options, (d) => d.query(script.query, arg, script.returns))
        }