Hello,

I am getting started in using the `cecile/mixed-dimensional`

branch. I have a 3D cube geometry with a cylindric hole at the center. I have defined the inner surface of the cylinder as a 2D subdomain using

```
> class Inner(SubDomain):
> def inside(self,x,on_boundary):
> tol = 1e-1
> return (on_boundary and np.linalg.norm(x[0:2]) <= ri + tol)
>
> marker = MeshFunction("size_t", mesh, mesh.topology().dim() - 1)
>
> marker.set_all(0)
> sm = Inner()
> sm.mark(marker, 1)
> marker = MeshFunction("size_t", mesh, mesh.topology().dim() - 1)
> submesh = MeshView.create(marker, 1)
```

My question is how do I map the vertex of the submesh to the parent mesh and vice-versa? Is there an easy way of doing this? I tried with some functions of MeshView but I can’t make it work.

Thank you!