SubIndices of SubEntities

It is rather inconvenient to get the SubIndices of an SubEntity, this for example needed to set dirichlet boundaries.

for i in grid.boundaryIntersections:
    e = i.inside
    geo = e.geometry
    indices = grid.indexSet.subIndices(e, 2)
    for j in e.domain.subEntities((i.indexInInside, 1), 2):
        A[indices[j]] *= 0
        A[indices[j], indices[j]] = 1
        b[indices[j]] = g(geo.corner(j))

It would be nice if there was a direct way to get the global indices of e.g. the vertices of an edge of a triangle.