(or homeomorphic to it?)
Here's what prompts this question. The way we draw a 3d cube on 2d paper is essentially the image of the cube's skeleton under a retract to a plane cross section of the 3d solid cube, right?
So, when someone makes a 3d model of a Klein bottle, are they doing something similar?
IE, can the 3d model be viewed as as the image of the boundary(?) of the Klein bottle's 4d embedding under a retract to one of the 3d cross-sections of the 4d embedding?