Drawing fundamental domains with sage

Question

What is the easiest way to draw fundamental domains for congruence subgroups of $SL_2(\mathbb{Z})$ in sage?

Answer 1

An easy way is to use FareySymbol. You can for example define the congruence subgroup $\Gamma_1(5)$ like this:

G = Gamma1(5)

Then use this to plot a fundamental domain:

FareySymbol(G).fundamental_domain()

This yields the following image: