Backend support for Layered Networks

[d-callan]

weve done good work recently introducing a Network class 🎉 but we would like to also support layered and temporal networks. my understanding is these two ideas are related in that a temporal network could be seen/ implemented as a type of layered network. but essentially were talking about a new class LayeredNetwork (or possibly two if we want a separate class and methods for TemporalNetwork, depending on use cases) w a slot called layers, which is a list of Network objects.

[d-callan]

image courtesy @asizemore

[asizemore]

lol image courtesy of this paper: https://www.researchgate.net/figure/Examples-of-multilayer-networks-A-A-network-of-web-pages-in-Wikipedia-can-be_fig2_319312216

To keep it true to the mathematical idea, id suggest a MutilayerNetwork class, then a TemporalNetwork subclass that has a few extra restrictions and assumptions