[new_pymtl] SignalValue minor doc cleanup
[new_pymtl] SignalValue minor doc cleanup

Abhinav117/pymtl,tj93/pymtl,jjffryan/pymtl,cornell-brg/pymtl,cfelton/pymtl,cornell-brg/pymtl,jjffryan/pymtl,cfelton/pymtl,jck/pymtl,12yujim/pymtl,Glyfina-Fernando/pymtl,cfelton/pymtl,Abhinav117/pymtl,12yujim/pymtl,Glyfina-Fernando/pymtl,jck/pymtl,12yujim/pymtl,jck/pymtl,tj93/pymtl,Glyfina-Fernando/pymtl,jjffryan/pymtl,Abhinav117/pymtl,tj93/pymtl,cornell-brg/pymtl,Abhinav117/pymtl