This is a dog leash I made of Mil-Spec Type 3 550 Paracord.

It's roughly 1,9 meters long and is made of 11+ meters of durable parachute cord.
A single strand of paracord can hold up to ~250kg of weight. (The snap hook is probably the weakest part of the leash. It's only tested for about 70kg, but that's still much weight. So this won't break easily). And at the same time the leash is rather light weight. Paracord only weights about 8 gram per meter.
So this leash can actually be used for big and smaller doggies. I made this one for a Yorkshire Terrier, but it would fit a shepherd dog as well.