No, I am not keen to steal a bike, just get the cable lock off a bike that's hanging in my garage... the lock is a thick Schwinn cable lock, no ID #. It takes a key and the key was long ago lost by my kids (or me... if I knew it wouldn't be lost!).

I can ride the bike with the cable still coiled-onto the top tube, but it would be nice to dump that pointless extra weight.

Lock looks like this one: https://www.amazon.com/Schwinn-Cable-.../dp/B0018CPG3U yeah the keys looked just like those

Says the guy whose avatar states "probably suspect".

If you clamp the cable in a vise to hold it steady a hacksaw will go through it in less time than it took me to type this.

cut the top tube, remove the lock, and reweld. nice thing about that method is that you can justify a new paint job or powder coat in the color of your choice.

Bolt cutters.

I idiotically locked my and my wife's bikes up together with a cable lock outside a country store, and only later realized that the keys were 7 miles away on my kitchen counter. Farmer Mike's bolt cutters saved the day. They cut through the cable like butter. I learned two important lessons that day:

1. Never buy a lock that you can lock without the key in hand.
2. Never rely on a cable lock to secure your bike from someone who wants to steal it. At best, they prevent opportunistic theft.

BTW his 30-inch bolt cutters worked like a charm, but my 24-inch cutters back home also slice through a cable easily. If the bolt cutters are too dull, they might not work, in which case a hacksaw is called for.

A locksmith can open it..

I have a friend, he was helpful when I lost the keys to my Apartment ,
keys went from in pocket, onto the street, somewhere..

with your teeth.

bolt cutters.

Thanks! I'm surprised that a bolt cutter would manage this but willing to take a shot. Cutting the tube: nah, this is a beater bike.

Light. Saber.

Craftsman Rotary Tool with a cutting wheel, safety goggles, and be very careful because it'll slice clean through whatever it touches.