code: def _fill_vao(self):
          
          with self.vao:
              self.vbos = []
              for loc, verts in enumerate(self.arrays):
                  vbo = VBO(verts)
                  self.vbos.append(vbo)
                  self.vao.assign_vertex_attrib_location(vbo, loc)
docs: Put array location in VAO for shader in same order as arrays given to Mesh.