Extracting mesh regions for gmsh mesh

[dokken]

Please either attach a minimal example, or have a look at: Transitioning from mesh.xml to mesh.xdmf, from dolfin-convert to meshio - #104 by dokken which explain how to extract multiple regions. I have also made a tutorial on the subject: Mesh generation and conversion with GMSH and PYGMSH | Jørgen S. Dokken