apt - Where can I find my original 'sources.list' file?

Note: If you have lost and want to recreate your /etc/apt/sources.list file, please use the Ubuntu Source Generator, with the appropriate choices. Warning: any custom repositories you added to your old sources.list (but not PPAs) will be lost.

Where can the original /etc/apt/sources.list be found?

I know some forum posts and third party sites pasting it's contents, but what is the official source for this file?

It must be somewhere on ubuntu.com?

It is generated by the installer.

If you use Ubiquity (the live one), you can see how in launchpad.

I didn't dig for the classic installer, debian-installer.