Cisco Modeling Labs (CML) is a tool specifically designed to create and simulate network topologies, allowing users to design, build, and test network configurations in a virtual environment. It is capable of running real Cisco images to provide an accurate simulation of Cisco and non-Cisco networks. Docker, pyATS, and Cisco DevNet Sandbox serve different purposes related to network automation and testing but are not primarily used for designing and simulating network topologies in the way CML is.