anchor: Mesh:getVertexMap
  Gets the vertex map for the Mesh. The vertex map describes the order in which the vertices are used when the Mesh is drawn. The vertices, vertex map, and mesh draw mode work together to determine what exactly is displayed on the screen.
  
  If no vertex map has been set previously via Mesh:setVertexMap, then this function will return nil in LÖVE 0.10.0+, or an empty table in 0.9.2 and older.
  map = Mesh:getVertexMap()
  map table A table containing the list of vertex indices used when drawing.