You should be able to translate the example used here Transitioning from mesh.xml to mesh.xdmf, from dolfin-convert to meshio directly to C++.
from dolfin import *
mesh = Mesh()
with XDMFFile("mesh.xdmf") as infile:
infile.read(mesh)
mvc = MeshValueCollection("size_t", mesh, 2)
with XDMFFile("mf.xdmf") as infile:
infile.read(mvc, "name_to_read")
mf = cpp.mesh.MeshFunctionSizet(mesh, mvc)
There are no functions used to load the mesh or mesh-function here that are python specific. They are just bindings to c++ functions.