Surface normal vector of a polygon in ArcGIS?

I have a dataset with 3D-Multipatch polygon features (roofs). My goal now is to determine different roof types, especially flat roofs. For this purpose I want to determine the surface normals for each polygon and store them in an attribute. Currently I determine this value by calculating the surface slope using a grid. Works well in principle, but I would like to avoid the detour via the grid calculation.

Is there a possibility in ArcGIS/ArcPy to perform the calculation directly?

For FME I have found a possibility in the FMEHub, but I would like to integrate the calculation directly into my script written in ArcPy.