Tom Gustafsson

Now the most obvious way of implementing this is to have two `FacetBasis` objects, one for the triangle facets and one for the quad facets, and then run `asm(form, [triangle_fbasis,...

I suggest we add also a convergence test for `ElementTetN0`. Could be a manufactured solution, any other suggestions?

Workaround: ```python m = MeshLine(np.linspace(0, 1, 100)) mp = MeshLine1DG.periodic(m, [99], [0]) ```

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