Retreiving the parent id in compose.js

Hi All

        How can we retrieve the parent id in initialize function of  the compose.js file in Email subpanel of Cases module.

I  have copied compose.js to  /<>/custom/modules/Emails/clients/base/views/compose.js and used

        console.log('parent id '+this.model.parent_id);

But this doesnt work.Can any one please help me. Prashant Patel Shijin Krishna

Regards

Sidhu