Duplicate clip

Hello,

I don't know how to duplicate clip in one sequence (of 2) which composed of several videotrack.

I have this script :

var first = app.project.rootItem.children[0];

first.setStartTime(20);

first.setInPoint(30);

first.setOutPoint(45);

var seq = app.project.activeSequence;

var vTrack1 = seq.videoTracks[1];

vTrack1.insertClip(first, '00;00;08;00');

This code will duplicate the clip 1 (children[0]) of the sequence 0 (rootTtem) on the sequence 1.

However, I would like to duplicate the clip 1 of the sequence 1 on the sequence 1.

I do not think I can use rootItem. I tried everything and do not know what to do

Do you know anything about that to destress me ?

Thank you