I want to use meshpy's tetgen interface to mesh a cube. I would like to enforce two types of constraints: first, I want some specified interior points to be included in the mesh; and second, I want some of those points to be connected with a mesh edge. The first of these can be done using the MeshInfo.set_points() method, and it seems there is support for the second type of constraint too, as MeshInfo has an attribute segment_constraints. Unfortunately, I have not been able to figure out how to use this. Could anyone give me a brief explanation of the intended way to use this, or alternatively an example?