Hello, Is it possible in firedrake to solve a BVP with periodic BCs on conforming meshes (symmetric nodes on opposite faces in case of a cubic unit cell)? I have a unit cell with random microstructure and a correpsonding periodic mesh at my disposal (generated from Netgen: https://ngsolve.org/) in Gmsh2 (.msh) format. Netgen/NGSolve<https://ngsolve.org/> Netgen/NGSolve is a high performance multiphysics finite element software. It is widely used to analyze models from solid mechanics, fluid dynamics and electromagnetics. ngsolve.org I am looking for something similar to https://fenicsproject.org/docs/dolfin/1.4.0/python/demo/documented/periodic/... except with the mesh instead of being a plain-unit square (cube) is a unit square (cube) with a bunch of holes inside. Is there a minimal example on how to crete subclasses just like it is done above in dolfin (demo_periodic.py), or otherwise, to illustrate implementation of Periodic BCs?